Patent Publication Number: US-8536745-B2

Title: Linear vibrator

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2010-0024861, filed on Mar. 19, 2010, entitled “LINEAR VIBRATOR”, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a linear vibrator. 
     2. Description of the Related Art 
     A vibration motor is a part which converts electric energy into mechanical vibration using the generating principle of electromagnetic force, and is mounted on a mobile phone to be used as a mute call indicating means. As the market for mobile phones is growing rapidly and a variety of functions are being added to the mobile phone, the parts of the mobile phone are being required to be miniaturized and of high quality. Thus, a new structure for a vibration motor, which overcomes the drawbacks of the conventional vibration motor and dramatically improves the quality of the conventional vibration motor, is required. 
     In recent years, as many mobile phones coming onto the market have large LCD screens and the mobile phones have adopted a touch screen manner, the use of a vibration motor to generate vibrations when a touch screen is touched has increased. Especially, the vibration motor for generating vibrations when the touch screen is touched must meet the following requirements. First, as the number of times the vibration motor is used to generate vibrations when the touch screen is touched is larger than the number of times the vibration motor is used to generate vibrations when a call is received, a long operating lifespan is required. Second, the vibrational response must become fast according to the speed at which the screen is touched, thus providing a high sense of satisfaction to the user who is touching the touch screen and feeling the vibrations. 
     A conventional vibration motor which has been widely used generates rotating force and rotates a rotary part using an eccentric mass, thus obtaining mechanical vibrations. The rotating force undergoes commutation through a contact point of a brush and a commutator, so that an electric current is supplied to a rotor coil. However, the brush type motor using the commutator is problematic in that, when the motor is rotated, the brush passes through a gap between segments of the commutator, thus causing mechanical friction and electric sparks, leading to abrasion, or generating impurities such as black powder and thereby shortening the lifespan of the motor. 
     Further, when a voltage is applied to the motor, it takes a long time to reach a target amount of vibrations because of the inertia of the rotary unit having the eccentric mass, so that the response becomes slow and thus it is difficult to realize vibrations suitable for a touch screen phone. 
     In order to overcome the drawbacks of lifespan and response and to realize the vibrating function of a touch screen phone, linear vibrators are widely used. 
     The linear vibrator does not use the rotating principle of a motor, but is excited by an electromagnetic force having a resonance frequency which is determined using a spring installed in the vibrator and a movable unit hanging on the spring, thus generating vibrations. Here, the electromagnetic force is generated when a magnet placed on a moving mass part interacts with the direct current or alternating current having a predetermined frequency of a coil placed on a support plate. 
     However, the linear vibrators which are being applied currently are generally located at the corner of a mobile phone, thus generating vibrations in a vertical direction relative to an LCD screen. The linear vibrator has an outer diameter of about 10 mm and a thickness of about 4 mm. However, the thickness of a linear vibrator designed to vibrate in a vertical direction is limited because a mass body installed in the vibrator must be able to be displaced vertically in a space having a thickness of about 4 mm in order to generate vibrations. Since the mounting space of a mobile phone is limited, using an increase in the thickness of the linear vibrator so as to obtain a desired amount of vibrations is limited. 
     In order to overcome the problems, the mass body in the linear vibrator may be constructed to move in a horizontal direction relative to the LCD screen of the mobile phone. The horizontal movement has a smaller spatial limitation, in comparison with the vertical movement. Further, it is relatively easy to realize a vibrator having a length of from 8 to 12 mm which is larger than the vertical thickness of about 4 mm. 
     Therefore, the present invention is intended to protect a coil lead wire from irregular movement when a mass body vibrates, in a linear vibrator constructed to have a thickness which is equal to or smaller than the conventional linear vibrator and constructed so that the mass body moves in a horizontal direction so as to improve a sensible amount of vibrations in a mobile phone. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a linear vibrator, which is capable of preventing abrasion and friction between a movable unit and a coil lead wire when a mass body vibrates. 
     In a linear vibrator according to an embodiment of the present invention, a mass body is accommodated in a casing defining the internal space of the linear vibrator and is vibrated. A bracket supports the linear vibrator from a lower position, and has a depression in a bottom thereof such that a coil lead wire of a coil is placed in the depression, thus preventing friction between the coil lead wire and a movable unit. 
     A depth of the depression may be larger than a thickness of the coil lead wire so that the coil lead wire is embedded in the depression, thus preventing friction between the coil lead wire and the movable unit. 
     Further, the bracket may further include a circuit board provided on an upper portion thereof for electric connection. 
     In a linear vibrator according to another embodiment of the present invention, a mass body is accommodated in a casing defining the internal space of the linear vibrator and is vibrated. A bracket supports the linear vibrator from a lower position, and has a protrusion in a bottom thereof such that a coil lead wire of a coil is placed in a space confined within the protrusion, thus preventing friction between the coil lead wire and a movable unit. 
     A height of the protrusion may be larger than a thickness of the coil lead wire so that the coil lead wire is embedded in the protrusion, thus preventing friction between the coil lead wire and the movable unit. 
     The protrusion may have a linear shape. 
     The bracket may further include a circuit board provided on an upper portion thereof for electric connection. 
     The bracket may further include a depression in the bottom thereof. 
     As is apparent from the above description, a linear vibrator according to the present invention provides an advantage in that a depression or a protrusion is formed in the bottom of a bracket, and a coil lead wire is placed inside the depression or the protrusion, thus preventing disconnection and abrasion resulting from a movable unit making contact with the coil lead wire when the linear vibrator is operated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and 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 an exploded perspective view illustrating a linear vibrator according to an embodiment of the present invention; 
         FIG. 2  is a perspective view illustrating a part of the linear vibrator of  FIG. 1 ; 
         FIG. 3  is an enlarged view illustrating a part of the linear vibrator of  FIG. 2 ; 
         FIG. 4  is a perspective view illustrating a part of a linear vibrator according to another embodiment of the present invention; and 
         FIG. 5  is an enlarged view illustrating a part of the linear vibrator of  FIG. 4 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The terms and words used in the present specification and claims should not be interpreted as being limited to typical meanings or dictionary definitions, but should be interpreted as having meanings and concepts relevant to the technical scope of the present invention based on the rule according to which an inventor can appropriately define the concept of the term to describe most appropriately the best method he or she knows for carrying out the invention. 
     The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. Herein, the same reference numerals are used throughout the different drawings to designate the same components. Further, when it is determined that the detailed description of the known art related to the present invention may obscure the gist of the present invention, the detailed description will be omitted. 
     Hereinafter, a linear vibrator according to the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
     As shown in  FIGS. 1 to 5 , a linear vibrator according to the present invention includes a casing  110 , a mass body  120 , an elastic member  130 , a yoke  140 , a magnet  150 , a coil  160 , a board  170  and a bracket  180 . 
     The casing  110  is an accommodating member having an internal space of a predetermined size, with the mass body  120 , a vibratory unit, and a stationary unit being provided in the casing  110 . 
     The mass body  120  interacts with the magnet  150  in response to the power signal of the coil  160 , thus generating linear vibrations. Here, the mass body  120  preferably has a specific gravity which is heavier than iron (Fe). This increases the mass of the vibrator for the same volume, thus adjusting a resonance frequency F related to the mass of the vibrator, and maximizing an amount of vibrations. 
     The mass body  120  is enlarged laterally to have a larger mass. Such a construction also increases the mass for a given volume, thus maximizing an amount of vibrations. 
     Generally, in the linear vibrator using a resonance frequency F, as shown in the following [Equation 1], the resonance frequency F is determined by the mass m of the mass body  120  and the elastic modulus k of the elastic member  130 . When power having the resonance frequency F is applied to the coil  160  and electric current flows in the coil  160 , the vertical displacement and vibration of the mass body  120  assume maximum values. 
     
       
         
           
             
               
                 
                   F 
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                       1 
                       
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                         k 
                         m 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     In order to correct the natural frequency of the linear vibrator  100 , the mass unit  120  is provided with at least one hole (not shown) to add to or subtract from the mass of the mass unit  120 . 
     One side of the elastic member  130  is attached to the mass body  120 , while the other side is attached to the casing  110 , thus elastically supporting the linear vibration of the mass body  120 . The elastic modulus of the elastic member  130  affects the natural frequency of the mass body  120 . 
     Further, the elastic member  130  is held in the internal space of the casing  110  in the form of a coil spring or a plate spring and is coupled to the mass body  120 , thus generating elastic force. 
     The yoke  140  is provided under the mass body  120  and the elastic members  130 , and receives the magnet  150  therein. The yoke  140  may uniformly induce the intensity of the magnetic field in cooperation with the magnet  150 . 
     The magnet  150  is placed in the coil  160  and interacts with an electric current flowing through the coil  160  to generate electromagnetic force in the direction of the central axis of the coil  160 . 
     When an electric current of a predetermined frequency is applied to the coil  160 , a magnetic field is induced around the coil  160 . The power signal of the coil  160  is applied to the mass body  120 , so that the mass body  120  interacts with the magnet  150  and thus generates linear vibrations of the mass body  120 . 
     Various electronic circuits and passive elements are mounted on the board  170  and connected to transceive electric signals. The board  170  is provided under the yoke  140 . 
     The bracket  180  is provided under the board  170 , thus supporting the parts of the linear vibrator  100  from a lower position. Here, the bracket  180  is made of a non-magnetic or weakly magnetic substance so as not to affect the drive unit. 
       FIG. 2  illustrates a depression  181  formed in the bottom of the bracket  180  of the linear vibrator  100  according to the present invention. 
     The depression  181  functions to prevent disconnection caused by the movable unit making contact with a coil lead wire  161  extended from an end of the coil  160  when the linear vibrator  100  is operated. The depth of the depression  181  must be larger than at least the thickness of the coil lead wire  161  so as to prevent friction between the coil lead wire  161  and the movable unit. 
       FIG. 3  is an enlarged view illustrating portion A of  FIG. 2 , wherein the coil lead wire  161  is embedded into the depression  181 . 
     The depression  181  is not limited to a specific shape and size, as long as the coil lead wire  161  may be embedded in the depression  181  such that friction does not occur between the coil lead wire  161  and other parts. 
       FIG. 4  illustrates a protrusion  182  which is provided on the bottom in a bracket  180  of a linear vibrator  100  according to the present invention. 
     The protrusion  182  functions to prevent disconnection caused by a movable unit making contact with a lead wire  161  of a coil  160  when the linear vibrator  100  is operated. The thickness of the protrusion  182  must be larger than at least the thickness of the coil lead wire  161  so as to prevent friction between the coil lead wire  161  and the movable unit. 
     The shape of the protrusion  182  is not limited to a specific shape. The protrusion  182  may protrude in a linear shape. 
       FIG. 5  is an enlarged view illustrating portion B of  FIG. 4 . Referring to the drawing, the coil lead wire  161  is placed in a space confined within the protrusion  182 . 
     Either of the depression  181  or the protrusion  182  may be provided in the bottom of the bracket  180 . However, if necessary, both the depression  181  and the protrusion  182  may be provided in the bottom of the bracket  180 . 
     The linear vibrator  100  according to the present invention is constructed so that the depression  181  or the protrusion  182  is formed in the bottom of the bracket  180 , and the coil lead wire  161  is placed in a space confined within the depression  181  or the protrusion  182 , thus preventing disconnection and abrasion caused by the movable unit making contact with the coil lead wire  161  when the linear vibrator  100  is operated. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.