Patent Publication Number: US-2013229083-A1

Title: Structure for Brushless Motors

Description:
(a) TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to an improved structure for brushless motors, and more particularly to an improved structure for brushless motors, which contains a uniform airgap, and can be operated smoothly and manufactured easily. 
     (b) DESCRIPTION OF THE PRIOR ART 
     In conventional brushless motors, since the airgap between the rotor and the stator is uneven, cogging or no-current torque would become more apparent in running the motor. Thus, those motors usually cannot be started or operated smoothly and would have significant vibration during operation, especially when they are employed in slower-running applications. Furthermore, since the magnetic flux distribution is not uniform in the airgap, the magnetic-field sensor mounted on the stator cannot measure the magnetic intensity appropriately, thereby causing more troubles in running the motor. 
     Thus, there is a need for providing an improved structure for brushless motors, which is easy to operate and manufacture, and has a uniform airgap. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide an improved structure for brushless motors, which contains a uniform airgap, and can be operated smoothly and manufactured easily. 
     To achieve the above object, a first embodiment of the improved structure for brushless motors is provided, which comprises a stationary part and a rotary part mounted outside of the stationary part and turning about the stationary part. The rotary part includes a frame and a plurality of magnets disposed, one after another, along an inner surface of the frame and attached to the inner surface adjacent to the stationary part, wherein each of the magnets has a curved surface so as to define a series of gaps between the curved surfaces of the magnets and the inner surface of the frame of the rotary part. The magnets are arranged, one after another, along the inner surface of the frame to form a ring of magnets, wherein the polarities of any two neighboring magnets are different. Since each magnet is configured with a curved surface adjacent to the inner surface of the frame, and the airgap between the magnets and the stationary part is uniform, the magnetic flux distribution in the airgap would be more uniform or sinusoidal. Thus, when running the motor, cogging or no-current torque can be reduced or eliminated, so that the motor can be operated more smoothly. 
     To achieve the above object, a second embodiment of the improved structure for brushless motors is further provided, which comprises a stationary part and a rotary part mounted inside of the stationary part and turning about the stationary part. The rotary part includes a frame and a plurality of magnets disposed, one after another, along an outer surface of the frame and attached to the outer surface adjacent to the stationary part, wherein each of the magnets has a curved surface so as to define a series of gaps between the curved surfaces of the magnets and the outer surface of the frame of the rotary part. With this embodiment, when running the motor, cogging or no-current torque can be reduced or eliminated, so that the motor can be operated more smoothly. 
     To achieve the above object, a third embodiment of the improved structure for brushless motors is still further provided, which comprises a stationary part and a movable part mounted at one side of the stationary part and linearly moving relative to the stationary part. The movable part includes a frame and a plurality of magnets disposed, one after another, along one surface of the frame and attached to the surface of the frame adjacent to the stationary part, wherein each of the magnets has a curved surface so as to define a series of gaps between the curved surfaces of the magnets and the surface of the frame of the movable part. With this embodiment, when running the motor, cogging or no-current torque can be reduced or eliminated, so that the motor can be operated more smoothly. 
     Other objects, advantages, and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a 3-dimensional assembled view of a first embodiment of the present invention. 
         FIG. 1A  is an enlarged 3-dimensional view, which partially shows the first embodiment. 
         FIG. 2  is an exploded view of the first embodiment. 
         FIG. 3  is a schematic view, which shows an operation of the first embodiment. 
         FIG. 3A  is an enlarged plan view, which partially show the first embodiment. 
         FIG. 4  is a schematic view, which partially shows an operation of the first embodiment. 
         FIG. 5  is a partially enlarged plan view of a second embodiment of the present invention. 
         FIG. 6  is a schematic plan view of the second embodiment. 
         FIG. 7  is a partially enlarged plan view of a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     To allow the features and advantages of the present invention to be fully understood, various embodiments with reference to the accompanying drawings will be illustrated in the following. 
     Referring to  FIGS. 1 ,  1 A,  2 ,  3 , and  3 A, a first embodiment of the present invention concerning an improved structure for brushless motors is disclosed, which comprises a stationary part  1  and a rotary part  2  mounted outside of the stationary part  1  and turning about the stationary part  1 . The rotary part  2  includes a frame  21  and a plurality of magnets  22  disposed, one after another, along an inner surface of the frame  21  and attached to the inner surface, adjacent to the stationary part  1 , by means of tight insertion or glue. Each of the magnets  22  has a first curved surface  221  and a second curved surface opposite to the first curved surface  221 , whereby a series of gaps  23  can be defined between the first curved surfaces  221  of the magnets  22  and the inner surface of the frame  21 , while a uniform airgap  24  can be defined between the second curved surfaces of the magnets  22  and the stationary part  1 . 
     In more detail, as shown in  FIG. 3 ,  3 A and  4 , the magnets  22  are arranged, one after another, along the inner surface of the frame  21  to form a ring of magnets, wherein the polarities of any two neighboring magnets are different. Since each magnet  22  is configured with the first curved surface  221  adjacent to the inner surface of the frame  21 , and the airgap  24  between the magnets  22  and the stationary part  1  is uniform, the magnetic flux distribution in the airgap  24  would be more uniform or sinusoidal. Thus, when running the motor of the present invention, cogging or no-current torque can be reduced or eliminated, so that the motor can be operated more smoothly. Furthermore, a magnetic-field sensor or a Hall-effect sensor (not shown) of the motor can measure the magnetic intensity more appropriately, thereby facilitating the operation of the motor. Still furthermore, the series of irregular gaps  23  may facilitate the magnets  22  to be attached to the frame  21  of the rotary part  2 , either by tight insertion or glue, so that the magnets  22  can be installed on the rotary part  2  more easily. Since the brushless motor of the present invention is simple in structure, easy to manufacture, and stable in operation, it can be applied in electric motorcycles, electric bikes, wind turbines, and other devices required for providing an output of high torque. 
     Turning now to  FIGS. 5 and 6 , a second embodiment of the present invention is disclosed, which comprises a stationary part  1   a  and a rotary part  2   a  mounted inside of the stationary part  1   a  and turning about the stationary part  1   a . The rotary part  2   a  includes a frame  21   a  and a plurality of magnets  22   a  disposed, on after another, along an outer surface of the frame  21   a  and attached to the outer surface, adjacent to the stationary part  1   a , by means of tight insertion or glue. Each of the magnets  22   a  has a first curved surface  221   a  and a second curved surface opposite to the first curved surface  221   a , whereby a series of gaps  23   a  can be defined between the first curved surfaces  221   a  of the magnets  22   a  and the outer surface of the frame  21   a , while a uniform airgap  24   a  can be defined between the second curved surfaces of the magnets  22   a  and the stationary part  1   a . In more detail, the magnets  22   a  are arranged, on after another, along the outer surface of the frame  21   a  to form a ring of magnets  22   a , wherein the polarities of any two neighboring magnets are different. This embodiment employs the same principles as the first embodiment, and thus has the same advantages, including simple structure, easy manufacturing, and stability in operation. 
     Referring to  FIG. 7 , a third embodiment of the present invention is disclosed, which comprises a stationary part  1   b  and a movable part  2   b  mounted at one side of the stationary part  1   b  and linearly moving relative to the stationary part  1   b . The movable part  2   b  includes a frame  21   b  and a plurality of magnets  22   b  disposed, one after another, along one surface of the frame  21   b  and attached to the surface of the frame  21   b , adjacent to the stationary part  1   b , by means of tight insertion or glue. Each of the magnets  22   b  has a first curved surface  221   b  and a second curved surface opposite to the first curved surface  221   b , whereby a series of gaps  23   b  can be defined between the first curved surfaces  221   b  of the magnets  22   b  and the surface of the frame  21   b , while a uniform airgap  24   b  can be defined between the second curved surfaces of the magnets  22   b  and the stationary part  1   b . In more detail, the magnets  22   b  are arranged, one after another, along the surface of the frame  21   b  to form a series of magnets  22   b , wherein the polarities of any two neighboring magnets are different. This embodiment employs the same principles as the first embodiment, and thus has the same advantages, including simple structure, easy manufacturing, and stability in operation. 
     As a summary, the present invention has the following advantages as compared with the prior art: 
     1. Since the magnets are each configured with a first curved surface adjacent to one surface of the frame of the rotary or movable part, and the airgap between the magnets and the stationary part is more uniform, the magnetic flux distribution in the airgap would be more uniform or sinusoidal. Thus, when running the motor, cogging or no-current torque can be reduced or eliminated, so that the motor can be operated more smoothly. 
     2. Since the airgap between the magnets and the stationary part is more uniform, the magnetic-field sensor of the motor can measure the magnetic intensity more appropriately, thereby facilitating the operation of the motor. 
     3. The series of irregular gaps between the magnets and the frame of the rotary or movable part allows the magnets to be attached to the frame of the rotary or movable part more easily, either by tight insertion or glue. 
     4. The brushless motor according to the present invention is simple in structure, easy to manufacture, and stable in operation, it can be applied in electric motorcycles, electric bikes, wind turbines, and other devices required for providing an output of high torque. 
     Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure is made by way of example only and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention hereinafter claimed.