Abstract:
A linear vibration motor includes: a top cover; a bracket coupled with the top cover to provide an internal space; a vibration unit having a mass body mounted at the internal space and linearly moving in a horizontal direction; an actuator having a magnet fixed to the mass body and a coil installed within a range of a magnetic field of the magnet and generating electromagnetic force to allow the vibration unit to move linearly in a horizontal direction; and a buffer member disposed in a space between the mass body and the bracket and limiting displacement of the vibration unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2009-0086035 filed on Sep. 11, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a linear vibration motor and, more particularly, to a linear vibration motor for vibrating a mass body in a horizontal direction within a mobile terminal and having a buffer member for the mass body. 
     2. Description of the Related Art 
     A vibration motor is a component for converting electric energy into mechanical vibrations by using the principle of the generation of electromagnetic force. The vibration motor, tending to become smaller and lighter, is employed in a mobile terminal to provide a mute (or silent) incoming call notification function or various vibration functions. 
     In particular, as mobile terminals have been reduced in size and have improved in quality, the use of a touch screen type LCD has been favored, requiring a function of generating vibrations when a touch is applied to the touch screen, so the improvement of the vibration motor has gradually taken place. 
     Recently, in order to implement a vibration function in touch screen phones, touch screen phones have employed a linear vibration motor. The linear vibration motor, rather than being based on the principle that a motor rotates, is excited by an electromagnetic force having a resonance frequency determined by using a spring installed within the linear vibration motor and a mass body hanging on the spring, to thereby generate vibrations. 
     Here, the electromagnetic force is generated by an interaction of a magnet positioned alongside the mass body in motion and a coil providing current of a certain frequency at a position corresponding to the magnet. 
     The linear vibration motor is configured to generate vibrations in a direction perpendicular to the LCD screen. However, in the case of vertical vibrations, a vertical displacement must be secured for the mass body to move to generate vibrations, resulting in a restriction in the thickness of the terminal. 
     Also, the reduction in the thickness of the terminal causes a problem in that the amount of vibrations produced by the vibration motor cannot be increased. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a linear vibration motor in which an internal mass body moves linearly in a horizontal direction and a buffer member is installed to support the horizontal, linear movement of the mass body and buffers the mass body. 
     According to an aspect of the present invention, there is provided a linear vibration motor including: a top cover; a bracket coupled with the top cover to provide an internal space; a vibration unit having a mass body mounted at the internal space and linearly moving in a horizontal direction; an actuator having a magnet fixed to the mass body and a coil installed within a range of a magnetic field of the magnet and generating electromagnetic force to allow the vibration unit to move linearly in a horizontal direction; and a buffer member disposed in a space between the mass body and the bracket and limiting displacement of the vibration unit. 
     The buffer member may be fixed to a coupling protrusion protruded from the mass body. 
     The buffer member may be fixed to a coupling protrusion protruded from the bracket. 
     The coupling protrusion may be thread-coupled with the buffer member. 
     The buffer member may be disposed at one side of the mass body, and an elastic member may be provided to the other side of the mass body in order to elastically support the vibration unit. 
     The elastic member may be a coil spring, a torsion spring, or a leaf spring. 
     The buffer member may be elastic rubber. 
     The linear vibration motor may further include: a fixed shaft extending from one side of the bracket or the mass body; and a buffer member support extending such that the buffer member is perpendicular to the fixed shaft, wherein an annular buffer member may be inserted into the buffer member support. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a partially cut-away perspective view of a linear vibration motor according to an exemplary embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of the linear vibration motor according to an exemplary embodiment of the present invention; 
         FIG. 3  is a schematic perspective view showing the interior of the linear vibration motor without a top cover according to an exemplary embodiment of the present invention; 
         FIG. 4  is a plan view of the linear vibration motor without the top cover according to an exemplary embodiment of the present invention; 
         FIG. 5  is a schematic perspective view showing the section of the linear vibration motor according to an exemplary embodiment of the present invention; 
         FIG. 6  is a schematic view showing a connection state of a buffer member of the linear vibration motor according to an exemplary embodiment of the present invention; 
         FIG. 7  is a schematic sectional view taken along line A-A of  FIG. 6 ; 
         FIG. 8  is a schematic view showing a connection state of a buffer member of the linear vibration motor according to another exemplary embodiment of the present invention; and 
         FIG. 9  is a schematic view showing a buffer member of the linear vibration motor according to another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the shapes and dimensions may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like components. 
       FIG. 1  is a partially cut-away perspective view of a linear vibration motor according to an exemplary embodiment of the present invention, and  FIG. 2  is an exploded perspective view of the linear vibration motor according to an exemplary embodiment of the present invention. 
       FIG. 3  is a schematic perspective view showing the interior of the linear vibration motor without a top cover according to an exemplary embodiment of the present invention,  FIG. 4  is a plan view of the linear vibration motor without the top cover according to an exemplary embodiment of the present invention, and  FIG. 5  is a schematic perspective view showing the section of the linear vibration motor according to an exemplary embodiment of the present invention. 
     With reference to  FIGS. 1 to 5 , a linear vibration motor  100  according to an exemplary embodiment of the present invention may include a top cover  140 , a bracket  110 , a vibration unit  120 , and a buffer member  164 . 
     The bracket  110  is coupled with the top cover  140  to provide an internal space. The bracket  110  has a structure in which an upper portion and a side portion thereof are open such that they correspond to the top cover  140 , and includes a bracket lower plate  112  and a support plate  114  in a widthwise direction. 
     A bobbin  150  is formed at an upper portion of the bracket lower plate  112 , and a circuit board  170  may be mounted thereupon. 
     The support plate  114  is formed to be bent vertically from the bracket lower plate  112 , and an elastic member  180  is insertedly fixed to one inner surface of the support plate  114 , and a buffer member  164  is provided on the other inner surface of the support plate  114 . 
     The bobbin  150  is positioned at the center of the upper portion of the bracket lower plate  112  and may include a vertical plate part  152  bent to be vertical to the bracket lower plate  112  and a cylindrical part  154  extending from the vertical plate part  152  such that it is horizontal to the bracket lower plate  112 . 
     The support plate part  152  and the cylindrical part  154  may have a hollow portion through which a magnet  132  moves reciprocally. 
     Here, a cylindrical coil  134  is insertedly fixed on an outer circumferential surface of the bobbin  150 , and the bobbin  150  has the cylindrical shape with a hollow portion therein allowing the magnet  132  to make a reciprocal movement therethrough. However, the structure of the bobbin  150  is not limited thereto, and the structure may be omitted. 
     The circuit board  170  is connected with an external input terminal and transfers power applied thereto to the cylindrical coil  134 . 
     However, the circuit board  170  is not limited to the configuration in which it is formed separately from the bracket  110 . Namely, the circuit board  170  and the bracket  110  may be integrally formed according to a designer&#39;s intention, and a flexible printed circuit board (FPCB) may be used as the circuit board  170 . 
     The cylindrical coil  134  serves to generate an electric field of a certain strength by interacting with the magnet  132  when power is applied thereto from an external source. The cylindrical coil  134  is inserted onto the outer circumferential surface of the cylindrical part  154  of the bobbin  150 . In this case, in fixing the cylindrical coil  134  to the cylindrical part  154 , a ring  136  is inserted to fix the cylindrical coil  134  to the cylindrical part  154 . 
     A coil line of the cylindrical coil  134  is connected with a pattern part of the circuit board  170  through soldering, whereby power can be applied to the cylindrical coil  134  from an external source. 
     However, the coil part is not limited to the cylindrical shape. Namely, a rectangular coil may be disposed on the upper surface of the bracket  110 , or a plate may be formed and disposed thereon. 
     The vibration unit  120  includes a mass body  126  mounted at the internal space of the bracket  110  and makes a horizontal linear movement due to an electromagnetic force of an actuating unit  130 . The mass body  126  may be mounted on a yoke part  124  which accommodates the cylindrical coil  134  and the magnet  132  therein. 
     The yoke part  124  configures a magnetic closed circuit by smoothly forming magnetic flux of the magnet  132  and may have internal space for accommodating the cylindrical coil  134  and the magnet  132  therein. 
     Both end portions of the yoke part  124  may be bent upward so as to be positioned perpendicular to the bracket lower pate  112 , and may extend to tightly attach on outer surfaces of the mass body  126 . 
     The mass body  126  serves to give a certain mass to the vibration unit  120  for linear vibrations, including an accommodation space for accommodating a central portion of the yoke part  124  therein. 
     Preferably, the mass body  126 , having a mass of a certain size, vibrates in a vibrational direction according to an interaction of the magnet  132  and the cylindrical coil  134 . Here, the vibrational direction refers to a direction horizontal to the cylindrical coil  134 . 
     The elastic member  180  elastically supports the vibration unit  120  such that the vibration unit  120  linearly moves horizontally. In a state that the elastic member  180  is fixed to the widthwise-directional support plate  114  of the bracket  110 , the other side thereof is fixed to the vibration unit  120 , thus elastically supporting the vibration unit  120 . 
     Here, the elastic member  180  may be a coil spring, a torsion spring, or a leaf spring. 
     Here, the elastic member  180  is disposed at one side of the vibration unit  120 , and the buffer member  164  is disposed at the other side of the vibration unit  120 . Specifically, the buffer member  164  is disposed in the space between the other side of the vibration unit  120  and the bracket  110  to limit the displacement of the vibration unit  120 . 
     Besides elastically supporting the vibration unit, the buffer member  164  may limit horizontal displacement. The buffer member  164  may be elastic rubber that absorbs an impact generated according to horizontal vibrations of the vibration unit  120 . 
     The buffer member  164  will now be described in detail. 
       FIG. 6  is a schematic view showing a connection state of the buffer member  164  of the linear vibration motor according to an exemplary embodiment of the present invention, and  FIG. 7  is a schematic sectional view taken along line A-A of  FIG. 6 . 
     With reference to  FIGS. 6 and 7 , the buffer member  164  may be fixed to a coupling protrusion  162  protruded from the mass body  126 . The buffer member  164  has a ball shape and coupled with the coupling protrusion  162 . 
     The coupling protrusion  162  includes a thread  164   a  formed thereon, and the buffer member  164  includes a thread  165   b  corresponding to the thread  164   a , whereby the mass body  126  and the buffer member  164  can be thread-coupled with each other. 
     The buffer member  164  may be in contact with the widthwise-directional support plate  114  of the bracket  110  or may be separated with a very small space therebetween. 
       FIG. 8  is a schematic view showing a connection state of a buffer member  160  of the linear vibration motor according to another exemplary embodiment of the present invention. 
     With reference to  FIG. 8 , the buffer member  164  may be fixedly thread-coupled with a coupling protrusion  162  protruded from the bracket  110 . For other constituents, the description of those in the exemplary embodiment illustrated with reference to  FIGS. 6 and 7  will be applied. 
       FIG. 9  is a schematic view showing a buffer member  166  of the linear vibration motor according to another exemplary embodiment of the present invention. 
     With reference to  FIG. 9 , the buffer member  166  has an annular shape, and may be inserted into a buffer member support  165  extending vertically from a fixed shaft  162  extending from one side of the bracket  110  or the mass body  126 . 
     As set forth above, in the linear vibration motor according to exemplary embodiments of the invention, the mass body vibrates in the horizontal direction, the thickness of a terminal is not restricted, and thus, the terminal can be fabricated so as to be slim. 
     Also, because the buffer member is provided at one side of the mass body, it can absorb an impact with respect to horizontal vibrations of the mass body, lengthening a life span of the linear vibration motor. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.