Patent Publication Number: US-2007108847-A1

Title: Cylinder-like electromagnetic motor

Description:
FIELD OF THE INVENTION  
      The present invention relates to a cylinder-like electromagnetic motor, and more particularly to an electromagnetic motor that has an actuating structure similar to that of a cylinder and provides the same function as a voice coil motor, but has less components, smaller volume, and simpler structure than the voice coil motor.  
     BACKGROUND OF THE INVENTION  
      A voice coil motor (VCM) has the advantages of small volume, low power consumption, accurately actuated displacement, and low price, and is very suitable for use as a short-distance actuator in many electronic products, such as the vibrating motor for a mobile phone, the vertical displacement actuator of a magnetic head or an optical pickup, the auto-focusing actuator for a camera, etc.  
       FIG. 1  is an exploded perspective view of a conventional voice coil motor used in a camera for auto focusing (AF). As shown, the voice coil motor mainly includes an upper cover  100 , a lower cover  105 , and an outer frame  110  having four inner wall surfaces provided with a magnet  115  each, an internally threaded lens holder  120  for a lens  125  to screw thereinto, a coil  130  wound around an outer side of the lens holder  120 , and an upper and a lower spring piece  135 . The lens holder  120  is supported by the upper and the lower spring piece  135  to movably locate in the outer frame  110  and be surrounded by the four magnets  115 .  
      When the coil  130  is supplied with a current to produce a magnetic field, the lens holder  120  and the four magnets  115  mutually repulse or attract to thereby produce a push force against the lens holder  120 . Since the lens holder  120  is supported by the spring pieces  135 , it is displaced forward or backward in the outer frame  110  by the push force.  
      The conventional voice coil motor has a relatively large overall volume and includes a lot of components that involve complicate assembling, and therefore requires increased manufacturing cost.  
      It is therefore tried by the inventor to develop an improved cylinder-like electromagnetic motor to overcome the disadvantages in the conventional voice coil motor.  
     SUMMARY OF THE INVENTION  
      A primary object of the present invention is to provide a structurally new cylinder-like electromagnetic motor that has reduced components and accordingly reduced overall volume to largely decrease the material and assembling cost of the motor.  
      Another object of the present invention is to provide a structurally new cylinder-like electromagnetic motor that has simplified structure and lowered power consumption, and operates in an even more active and rapid manner.  
      To achieve the above and other objects, the cylinder-like electromagnetic motor of the present invention includes a base having a closed-bottom central hole; a cover connected to the top of the base; a spring piece located between the cover and the top of the base; a holder movably received in the central hole of the base; a magnetic element fitted to a bottom of the central hole of the base to locate below the holder; an electromagnetic element fitted below the magnetic element. Due to an electromagnetic field effect between the magnet element and the electromagnetic element, the holder located above the magnetic element is pushed forward or backward in the base. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein  
       FIG. 1  is an exploded perspective view of a conventional voice coil motor;  
       FIG. 2  is an exploded perspective view of a cylinder-like electromagnetic motor according to a preferred embodiment of the present invention; and  
       FIG. 3  is a sectional view of the cylinder-like electromagnetic motor of  FIG. 2  in an actuated state. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Please refer to  FIG. 2  that is an exploded perspective view of a cylinder-like electromagnetic motor according to a preferred embodiment of the present invention. As shown, the cylinder-like electromagnetic motor of the present invention includes a base  10 , a spring piece  20 , a cover  30 , a holder  40 , a magnetic element  50 , and an electromagnetic element  60 . The base  10  is provided with a closed-bottom central hole  11 , in which all other components  20 ,  30 ,  40 ,  50 , and  60  of the electromagnetic motor are received. Since the base  10  has a reduced volume as compared with the conventional voice coil motor, the electromagnetic motor of the present invention may have a relatively small overall volume. The cover  30  is fixedly connected to a top of the base  10 .  
      The spring piece  20  is located between the cover  30  and the top of the base  10 , and is provided at predetermined positions with a plurality of curved narrow openings to be divided into a movable inner portion and a fixed outer portion. The movable inner portion of the spring piece  20  is screwed to the holder  40 , and the fixed outer portion of the spring piece  20  is screwed to the top of the base  10 . The holder  40  is movably supported in the central hole  11  of the base  10  due to the spring piece  20  that is connected at the movable inner portion to the holder  40  and at the fixed outer portion to the base  10 . The holder  40  is internally threaded for a lens  125  to screw thereinto. Since the spring piece  20  is actually a plate spring, it provide relatively good elasticity and restoring force, enabling the holder  40  to have a large moving distance relative to the base  10 .  
       FIG. 3  is a sectional view showing the cylinder-like electromagnetic motor of the present invention in an actuated state. As shown, the electromagnetic element  60  is located at a bottom of the central hole  11  of the base  10 , and the magnetic element  50  is disposed on a top of the electromagnetic element  60  and immediately below the holder  40 . When a current is supplied to the electromagnetic element  60 , an electromagnetic field is produced, causing the electromagnetic element  60  and the magnetic element  50  to mutually attract or repulse to thereby produce a push force against the holder  40  for the latter to move forward or backward. Reversely, when the current supplied to the electromagnetic element  60  is cut off, the produced electromagnetic field vanishes, and the restoring force of the spring piece  20  automatically pushes the holder  40   10  and the magnetic element  50  backward to their initial position in the base  10 . In the preferred embodiment of the present invention, the magnetic element  50  is a magnet, and the electromagnetic element  60  is an electromagnet.  
      Both the spring piece  20  and the cover  30  are provided with a central hole corresponding to the central hole  11  on the base  10 , and the spring piece  20  is preferably mounted on and around a top peripheral area of the holder  40 , so that the lens  125  may be screwed into the holder  40  via the central holes of the cover  30  and the spring piece  20 .  
      From a comparison of  FIG. 2  with  FIG. 1 , it is found the electromagnetic motor of the present invention omits the lower cover  105 , the lower spring piece  135 , and three magnets  115  that are included in the conventional voice coil motor. Meanwhile, the base  10  and the magnet element  50  in the present invention have volumes smaller than that in the conventional voice coil motor. Since the electromagnetic motor of the present invention has fewer components and relatively reduced volume, it requires less material and can therefore be produced at lowered cost.  
      The electromagnetic motor of the present invention applies an actuating principle different from that of the conventional voice coil motor. In the voice coil motor, fixed magnets are located around an inner movable coil to produce a magnetic field and accordingly an actuating force. However, in the present invention, a fixed electromagnet is located below a movable magnet to produce an electromagnetic field and accordingly a forward push force or a backward attraction force, just like the motion of a cylinder in an automobile to produce power at the bottom of the cylinder.  
      The present invention has been described with a preferred embodiment thereof and it is understood that many changes and modifications in the described embodiment can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims.