Abstract:
A DC brushless voice-coil vibration motor, especially a small-sized micro-vibration motor that utilizes inductance coils and a weight object with a plurality of coplanar magnetic poles as the stator and rotor of the motor. The invention comprises a circuit board, at least two inductance coils and a weight object. The weight object is installed on the inductance coil and away from the motor center. It has a plurality of magnetic poles as the rotor of the motor. When current flows through the inductance coil, a magnetic field is generated so that the weight object starts to rotate under the electromagnetic interactions. Since the weight object is off the motor center, the motor gains vibrational energy during the rotation of the weight object.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to a DC brushless voice-coil vibration motor. By changing the designs of the stator and rotor in a motor, a miniaturized DC brushless voice-coil vibration motor can gain vibrational energy by having the rotor installed off the motor center. 
     2. Related Art 
     The mobile phone can provide on-to-one distant communication. Due to its small volume and light weight, it has become one of the most popular high-tech electronics of the century. 
     Usually, notifying the user incoming messages can be achieved by two methods: the ring-on mode and the vibration mode. In the ring-on mode, the mobile phone turns on ring or music when there is an incoming message. In the vibration mode, a vibration motor installed in the mobile phone starts to vibrate when an incoming message is received so that the user can feel the vibration of the mobile and answer the phone call. 
     The currently available vibration motor is shown in, for example, FIG.  1 . The vibration motor has a cylindrical shape with a weight attached to the motor axis. When the motor rotates, the weight also rotates to generate vibrational energy. However, as the electronics such as notebook computers, PDA&#39;s (Personal Digital Assistant), mobile phones become lighter, thinner, shorter and smaller, the volume occupied by the conventional vibration motor greatly limits the designs of these high-tech electronics. 
     To minimize all electronic components in the vibration motor will be ideally an attempt to decrease its volume. Nevertheless, such an idea is not feasible because there might be difficulty in assembly after the miniaturization. Such limitations render the problems that are bound to be encountered after the miniaturization of the motor. Even if the assembly is possible, the difficulty in assembly may increase the cost. 
     Furthermore, the vibration is generated by attaching a weight to one end of the motor axis. Therefore, the dimensions of the weight object define the size of motor. As shown in FIG. 1, the weight is situated on one side of the motor, the part that generates vibrational energy is just ¼of the whole motor. The vibration is thus local but not global. The motor has to output a larger power so as to rotate the weight and thereby increasing unnecessary power consumption. Since the weight object is fixed on the motor axis, the output vibration efficiency is also fixed. So one has to use different motors on different models of electronics in order to generate desired vibration. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, the invention provides a miniaturized DC brushless voice-coil vibration motor. It mainly consists of a circuit board, at least two inductance coils, a weight object, a controller and at least two magnetic bolts. The inductance coils are installed on the circuit board by winding around in the radial direction and is electrically connected to the power input port on the circuit board. The magnetic bolts are situated between the two inductance coils. The weight object is installed on the inductance coils, slightly off the motor center. It is a permanent magnet with a plurality of coplanar magnetic poles. The controller installed on the circuit board between the two inductance coils functions to change the magnetic properties of the inductance coils, determining whether the motor is on or off. When current pass through the inductance coils and generates a magnetic field, the magnetic bolts disturb the static balance of the magnetic field inside the motor. Under the electromagnetic interactions between the inductance coils and the weight object, the weight object rotates and gains rotational energy. Since the weight object is displaced off the motor center, the rotational energy of the weight object turns into vibrational energy of the motor. 
     The weight object functions as the rotor inside the motor and generates vibrational energy so that the motor can generate vibrational energy in all directions. It lowers the power consumption when starting the motor and increases the operational efficiency of the vibrational motor. 
     The weight object in the invention can have different displacements from the motor center to generate different vibration levels for different models of electronics. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become fully understood from the detailed description given hereinbelow for illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a schematic view of a traditional vibrational motor; 
     FIG. 2 is a three-dimensional exploded view of the invention; 
     FIG. 3 is a three-dimensional perspective of an assembled embodiment; 
     FIG. 4 is a side cross-sectional view of an assembled embodiment; 
     FIG. 5 is a schematic view of the magnetic poles on the magnetic weight object; 
     FIG. 6 is a schematic view of the main circuit of the invention; and 
     FIGS. 7 and 8 are schematic views showing the relation between the magnetic weight object and the sleeve. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIGS. 2 and 3, the disclosed DC brushless voice-coil vibration motor  10  includes a shell  11 , a circuit board  12 , a shaft  13 , two inductance coils  14   a ,  14   b , a controller  15 , a protective ring  16 , two magnetic bolts  17   a ,  17   b , and a weight object  18 . The shell  11  covers the other components in the DC brushless voice-coil vibration motor  10  and is an ellipsoid comprised of a base  111  and a top cover  112 . Since the DC brushless sonic vibration motor  10  uses electrical power to generate magnetic energy which then converts into mechanical energy, the shell  11  therefore has to be made of a non-magnetic material such as aluminum, nickel, copper or plastic, avoiding disturbinging the inductance magnetic field in the motor  10 . An opening  1122  is formed at the bottom of the side surface of the top cover  112 . 
     The circuit board  12 , the shaft  13 , the inductance coils  14   a ,  14   b , the controller  15 , the protective ring  16 , the two magnetic bolts  17   a ,  17   b , and a magnetic device  18  are installed from bottom to top inside the shell  11 . The circuit board  12  is a print circuit board with a print circuit on it. Since most electrical properties (e.g., changing current direction and driving magnetic interactions) in the motor  10  are designed to be controlled by the controller  15 , the print circuit on the print circuit board  12  will not be too complicated to implement (see FIG. 6 for a schematic view of the main circuit). Thus, the manufacturing cost can be lowered. The circuit board  12  is installed inside the shell  11  and is therefore circular with an electrical port  121  protruded from one side. Power input points  1211 ,  1212  are provided on the electrical port  121 . An external power source (not shown) connects to the power input points  1211 ,  1212  to provide the power needed for the motor operation. The electrical port  121  extends outside the shell  11  from the side opening  1122  of the top cover  112  in order to connect to the external power source. The shaft  13  is installed at the center of the circuit board  12 . 
     The two inductance coils  14   a ,  14   b  are formed by winding conductive wires in the radial direction and installed on opposite sides of the circuit  12 , with electrical connection to the print circuit on the circuit board  12  (FIG.  6 ). They function as the stators in the motor  10 . According to the Ampere&#39;s right-hand rule, if the electrical current is in the radial direction, the magnetic filed is in the axial direction. Thus, when a current flows through the inductance coils  14   a ,  14   b , they generate a magnetic field in the axial direction. 
     The controller  15  is a micro-processing IC installed on the circuit board  12  with electrical connection to the print circuit (FIG.  6 ). The controller  15  integrates the components for most of the necessary electrical properties (e.g., changing the current direction and driving magnetic interactions) for the motor  10 , thereby controlling the vibration of the motor  10 . The main purpose of this design is to simplify the electrical components needed by the circuit inside the motor  10 . The print circuit on the circuit board  12  can thus be simplified, which is most convenient for the assembly of miniaturized DC brushless voice-coil vibration motor  10 . 
     The protective ring  16  is made of non-magnetic material such as plastic so as to avoid disturbing the magnetic field inside the motor  10 . It has a first through hole  161  and a second through hole  162  corresponding to the inductance coils  14   a ,  14   b , respectively, a third through hole  163  at the motor center corresponding to the shaft  13 , a fourth through hole  164  corresponding to the controller  15 , and a fifth through hole  165  and a sixth through hole  166  formed between the first through hole  161  and the second through hole  162 . The height of the protective ring  16  is equal to the size of the inductance coils  14   a ,  14   b . The inner diameter of the first through hole  161  and the second through hole  162  is equal to the coil diameter of the inductance coils  14   a ,  14   b . The protective ring  16  is installed on the circuit board  12 . The shaft  13  penetrates through the third through hole  163 . The inductance coils  14   a ,  14   b  are installed inside the first through hole  161  and the second through hole  162 , respectively. The controller  15  is installed on the fourth through hole  164 . Installing inductance coils  14   a ,  14   b  inside the first through hole  161  and the second through hole  162  keeps the winding pattern of the inductance coils  14   a ,  14   b  unchanged. The magnetic bolts  17   a ,  17   b  are installed inside the fifth through hole  165  and the sixth through hole  166 , respectively. 
     The magnetic bolts  17   a ,  17   b  are made of ferromagnetic material, such as iron. They are made into cylindrical shapes that exactly fit into the fifth through hole  165  and the sixth through hole  166 . 
     The weight object  18  is a permanent magnet in a disk shape. A plurality of magnetic poles  181 ,  182 ,  183 ,  184  is formed on separate areas within the same plane (FIG. 4) as the rotors of the motor  10 . The two adjacent poles have opposite magnetic properties (one being an N pole and the other an S pole). The magnetic lines of the magnetic poles  181 ,  182 ,  183 ,  184  are axial, acting on the inductance coils  14   a ,  14   b . When the inductance coils  14   a ,  14   b  generate magnetic forces, the weight object  18  repels from the inductance coils  14   a ,  14   b  to rotate. A magnetic sleeve  19  is attached to the weight object  18  by the magnetic attraction. It is attached to the top of the weight object  18  and rotates along with the weight object, avoiding the generation of friction due to direct contact between the weight object  18  and the shell  11 . To generate vibration, the weight object  18  is installed eccentric to the center of the sleeve  19 . That is, the center of the sleeve  19  and the center of the weight object  18  are not on the same axis (FIG.  7 ). Therefore, vibration can be induced during the rotation of the weight object  18 . 
     With reference to FIGS. 4 and 6, the external power source connects to the power input points  1211 ,  1212 , which then connect to the inductance coils  14   a ,  14   b . The inductance coils  14   a ,  14   b  are also in electrical connection with the controller  15  to form a close electrical loop. The weight object  18  are magnetically coupled with the magnetic bolts  17   a ,  17   b  so that the magnetic bolts  17   a ,  17   b  become temporary magnetic bolts. When the external power generates current through the power input points  1211 ,  1212 , the current flows through the inductance coils  14   a ,  14   b  to generate a magnetic field. The magnetic bolts  17   a ,  17   b  disturb the static balance of the magnetic field. The inductance coils  14   a ,  14   b  repel from the weight object  18  so that the weight object  18  begins to rotate. Due to the fact that the weight object is off the motor center, the rotational energy is converted into vibrational energy of the motor. 
     As shown in FIG. 8, the relative position of the weight object  18  and the sleeve  19  can be adjusted to generate different vibration level. Therefore, by modifying the displacement between them, the invention can be adjusted to produce the desired vibration without modifying or adding other components. 
     Effects of the Invention 
     As described before, the DC brushless voice-coil vibration motor proposed in the disclosure is a miniaturized motor. By modifying the structure of the stators and rotors inside the motor and the off-center design for the rotors, the disclosed invention can achieve the object of generating required vibration while having a miniaturized structure. 
     The invention directly uses the rotor as the weight object needed for generating vibration, avoiding the load of an additional weight as in the prior art. This can greatly increase the efficiency of the motor operation. 
     Furthermore, the invention can achieve to generate different vibration levels by simply changing the displacement of the weight object relative to the center of motor rather than redesigning the weight object for every desired vibration level of the vibration motor in the prior art. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.