[0001]    This application claims the priority of Korean Patent Application No. 10-2013-0026516 filed on Mar. 13, 2013, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a linear vibrator able to be mounted in small electronic devices, and more particularly, to implementation of a small and light horizontal linear vibrator. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, one of the fundamental functions of communications devices is the call notification function. Examples thereof may include a sound generation function, such as melody or bell and a vibration function, in which vibrations are transferred to devices. 
         [0006]    Among these functions, the vibration function has mainly been used to prevent a melody or a bell provided through a speaker of a device from inconveniencing others. 
         [0007]    In order to implement the vibration function, generally, vibratory force, generated by driving a small vibration motor, is transferred to a case to allow devices to be vibrated. 
         [0008]    In recent times, as demand for small and multifunctional mobile phone has increased, a touch screen type display device, or the like, has been frequently adopted. However, there is a need to increasingly improve vibration motors to have a function of generating vibrations when the display device is touched, and the like. 
         [0009]    Vibration motors used in existing mobile phones employ a method of generating a torque to rotate a rotating part of an unbalance mass so as to obtain mechanical vibrations. In this case, the torque is mainly generated by a structure in which a current commutated through a contact between a brush and a commutator is supplied to a rotor coil. 
         [0010]    However, a brush-type structure using the commutator causes mechanical friction and generates electrical sparks, while the brush passes through a gap between segments of the commutator at the time of rotating the motor and therefore wears the brush and the commutator, thereby shortening the lifespan of the motor. 
         [0011]    Further, rotational inertia may be present in the brush-type structure when voltage is applied to the motor, thus requiring a relatively long period of time to reach a targeted vibration amount, and therefore, it may be difficult to implement an amount of vibrations appropriate for personal digital assistants (PDAs), and the like, to which the touch screen is applied. 
         [0012]    Therefore, in order to improve lifespan and response characteristics of the display device, a linear vibrator generating vibrations through a scheme other than a rotational scheme has been used. 
         [0013]    Such a linear vibrator uses a spring mounted therein and a mass body coupled to the spring, having a determined resonance frequency and excited by electromagnetic force, to thereby generate vibrations. 
         [0014]    However, since the linear vibrator may be vibrated vertically and only generates vibrations in the case in which the linear vibrator moves, securing a vertical displacement of the mass body mounted therein, the linear vibrator may have a restriction in terms of a thickness. 
         [0015]    Further, since the thickness of the linear vibrator increases with the increase in the amount of vibrations generated thereby, PDAs require a large space to allow the linear vibrator to be mounted therein, such that it is difficult to miniaturize the linear vibrator. 
         [0016]    Meanwhile, as the related art, there are provided Patent Documents 1 and 2. Both of Patent Documents 1 and 2 disclose a linear vibrator. However, Patent Document 1 does not have a configuration allowing for a stable reciprocating motion to be induced in a vibration part, such that it is difficult to obtain a constant vibrational frequency. On the other hand, according to Patent Document 2, a constant vibrational frequency may be obtained by a shaft guiding a reciprocating motion of the vibration part. However, according to Patent Document 2, since the shaft and the vibration part may not be easily assembled and the shaft may be easily deformed due to external impacts, the miniaturization and lightness of the linear vibrator may not be easily implemented and the linear vibrator may be inappropriate for portable electronic devices to which external impacts are frequently applied. 
       RELATED ART DOCUMENT 
       [0000]    
       
         (Patent Document 1) KR10-1152417 B1 
         (Patent Document 2) JP2012-016153 A 
       
     
       SUMMARY OF THE INVENTION 
       [0019]    An aspect of the present invention provides a horizontal linear vibrator which can be easily miniaturized, is reduced in weight and can withstand external impacts. 
         [0020]    According to an aspect of the present invention, there is provided a horizontal linear vibrator, including: a housing; 
         [0021]    a mass member movably mounted within the housing in a length direction thereof; a coil member mounted in the housing; a magnet member mounted in the mass member and interacting with the coil member to generate a magnetic field so as to enable movement of the mass member; an elastic member mounted in the housing and applying force in the same direction as or an opposite direction to a moving direction of the mass member; and a bearing member disposed between the mass member and the housing to enable a sliding motion of the mass member relative to the housing. 
         [0022]    The elastic member may be a coil spring. 
         [0023]    The elastic member may include: a first spring connecting one end of the housing to one end of the mass member; and a second spring connecting the other end of the housing to the other end of the mass member. 
         [0024]    The first spring and the second spring may have different spring constants. 
         [0025]    The housing may have a cylindrical shape having a circular cross-section, and the mass member may have a cylindrical shape having a circular cross-section. 
         [0026]    The magnet member may be disposed to be deflected in one direction from a center of a magnetic field of the coil member to provide a deflected magnetic field to the coil member in a state in which the mass member stops. 
         [0027]    According to an aspect of the present invention, there is provided a horizontal linear vibrator, including: a housing; a mass member movably mounted within the housing in a length direction thereof; a magnet member mounted in the housing; a coil member mounted in the mass member and interacting with the magnet member to generate a magnetic field so as to enable movement of the mass member; an elastic member mounted in the housing and applying force in the same direction as or an opposite direction to a moving direction of the mass member; and a bearing member disposed between the mass member and the housing to enable a sliding motion of the mass member relative to the housing. 
         [0028]    The elastic member may be a coil spring. 
         [0029]    The elastic member may include: a first spring connecting one end of the housing to one end of the mass member; and a second spring connecting the other end of the housing to the other end of the mass member. 
         [0030]    The first spring and the second spring may have different spring constants. 
         [0031]    The housing may have a cylindrical shape having a circular cross-section and the mass member may have a cylindrical shape having a circular cross-section. 
         [0032]    The magnet member may be disposed to be deflected in one direction from a center of a magnetic field of the coil member to provide a deflected magnetic field to the coil member in a state in which the mass member stops. 
         [0033]    According to an aspect of the present invention, there is provided a horizontal linear vibrator, including: a housing provided with a groove extending lengthily in a length direction; amass member movably mounted within the housing in a length direction thereof and provided with a protrusion inserted into the groove; a coil member mounted in the housing; a magnet member mounted in the mass member and interacting with the coil member to generate a magnetic field so as to enable movement of the mass member; and an elastic member mounted in the housing and applying force in the same direction as or an opposite direction to a moving direction of the mass member. 
         [0034]    The elastic member may be a coil spring. 
         [0035]    The elastic member may include: a first spring connecting one end of the housing to one end of the mass member; and a second spring connecting the other end of the housing to the other end of the mass member. 
         [0036]    The first spring and the second spring may have different spring constants. 
         [0037]    The housing may have a cylindrical shape having a circular cross-section and the mass member may have a cylindrical shape having a circular cross-section. 
         [0038]    The magnet member may be disposed to be deflected in one direction from a center of a magnetic field of the coil member to provide a deflected magnetic field to the coil member in a state in which the mass member stops. 
         [0039]    According to an aspect of the present invention, there is provided a horizontal linear vibrator, including: a housing having a receiving space extending in a length direction; amass member mounted in the receiving space and movable along the length direction; a coil member mounted in the housing; a magnet member mounted in the mass member and interacting with the coil member to generate a magnetic field so as to enable movement of the mass member; and an elastic member mounted in the housing and applying force in the same direction as or an opposite direction to a moving direction of the mass member, wherein the receiving space has an asymmetrical cross-section or an oval or polygonal cross-section and the mass member has a cross-sectional shape coinciding with a section of the receiving space. 
         [0040]    The elastic member may be a coil spring. 
         [0041]    The elastic member may include: a first spring connecting one end of the housing to one end of the mass member; and a second spring connecting the other end of the housing to the other end of the mass member. 
         [0042]    The first spring and the second spring may have different spring constants. 
         [0043]    The magnet member may be disposed to be deflected in one direction from a center of a magnetic field of the coil member to provide a deflected magnetic field to the coil member in a state in which the mass member stops. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]    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: 
           [0045]      FIG. 1  is a cross-sectional view of a horizontal linear vibrator according to a first embodiment of the present invention; 
           [0046]      FIG. 2  is a cross-sectional view taken along line A-A of the horizontal linear vibrator illustrated in  FIG. 1 ; 
           [0047]      FIG. 3  is a cross-sectional view illustrating another form of the horizontal linear vibrator illustrated in  FIG. 1 ; 
           [0048]      FIG. 4  is a cross-sectional view of a horizontal linear vibrator according to a second embodiment of the present invention; 
           [0049]      FIG. 5  is a cross-sectional view of a horizontal linear vibrator according to a third embodiment of the present invention; 
           [0050]      FIG. 6  is a cross-sectional view taken along line B-B of the horizontal linear vibrator illustrated in  FIG. 5 ; 
           [0051]      FIGS. 7 and 8  are cross-sectional views of another form of the horizontal linear vibrator taken along line B-B illustrated in  FIG. 5 ; 
           [0052]      FIG. 9  is a cross-sectional view of a horizontal linear vibrator according to a fourth embodiment of the present invention; 
           [0053]      FIG. 10  is a cross-sectional view taken along line C-C of the horizontal linear vibrator illustrated in  FIG. 9 ; and 
           [0054]      FIGS. 11 and 12  are cross-sectional views of another form of the horizontal linear vibrator taken along line C-C illustrated in  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0055]    Hereinafter, embodiments of the present invention will 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. 
         [0056]    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. 
         [0057]      FIG. 1  is a cross-sectional view of a horizontal linear vibrator according to a first embodiment of the present invention;  FIG. 2  is a cross-sectional view taken along line A-A of the horizontal linear vibrator illustrated in  FIG. 1 ;  FIG. 3  is a cross-sectional view illustrating another form of the horizontal linear vibrator illustrated in  FIG. 1 ;  FIG. 4  is a cross-sectional view of a horizontal linear vibrator according to a second embodiment of the present invention;  FIG. 5  is a cross-sectional view of a horizontal linear vibrator according to a third embodiment of the present invention;  FIG. 6  is a cross-sectional view taken along line B-B of the horizontal linear vibrator illustrated in  FIG. 5 ;  FIGS. 7 and 8  are cross-sectional views of another form of the horizontal linear vibrator taken along line B-B illustrated in  FIG. 5 ;  FIG. 9  is a cross-sectional view of a horizontal linear vibrator according to a fourth embodiment of the present invention;  FIG. 10  is a cross-sectional view taken along line C-C of the horizontal linear vibrator illustrated in  FIG. 9 ; and  FIGS. 11 and 12  are cross-sectional views of another form of the horizontal linear vibrator taken along line C-C illustrated in  FIG. 9 . 
         [0058]    The horizontal linear vibrator according to a first embodiment of the present invention will be described with reference  FIGS. 1 through 3 . 
         [0059]    A horizontal linear vibrator  100  according to the embodiment of the present invention may include a housing  110 , a mass member  120 , a magnet member  130 , and a coil member  140 . In addition, the horizontal linear vibrator  100  may further include an elastic member  150  and a bearing member  160 . 
         [0060]    The housing  110  has a receiving space  112  and may be formed to lengthily extend in one direction. For example, the housing  110  may have a hollow cylindrical shape (see  FIG. 2 ). However, the shape of the housing  110  is not limited to the cylindrical shape. In other words, the housing  110  may have a polygonal shape or other shapes, as necessary. 
         [0061]    The housing  110  may be formed of a material having sufficient rigidity to protect members disposed in the receiving space  112  from external impact. For example, the housing  110  may be formed of a metal or a plastic material. However, the housing  110  is not only formed of the above-mentioned materials, but may be formed of other materials, as needed. 
         [0062]    The housing  110  may be formed of a plurality of members. In other words, the housing  110  may be formed by coupling two members which are symmetrical, relative to each other. By this configuration, the plurality of members may easily be mounted in the receiving space  112  of the housing  110  and the mounted members may easily be replaced and exchanged with other members. 
         [0063]    The mass member  120  may be mounted in the receiving space  112  of the housing  110 . In other words, the mass member  120  has a size smaller than that of the housing  110 , and therefore may be completely received in the receiving space  112 . For reference, according to the embodiment of the present invention, the mass member  120  has a cylindrical shape which substantially coincides with the receiving space  112  of the housing  110 . However, the shape of the mass member  120  is not limited to a cylinder, but may be changed variously, as needed. 
         [0064]    The mass member  120  may move in the receiving space  112 . In other words, the mass member  120  may move in a reciprocal manner in a length direction of the housing  110 . To this end, a length L1 of the mass member  120  may be shorter than a length of the housing  110  or a length L2 of the receiving space  112 . In this case, a length deviation L2-L1 between the length L2 of the receiving space  112  and the length L1 of the mass member  120  may be determined depending on a type of a natural vibrational frequency of the horizontal linear vibrator  100 . For example, when the natural vibrational frequency having relatively large amplitude is required, the length deviation L2-L1 may be large and when the natural vibrational frequency having relatively small amplitude is required, the length deviation L2-L1 may be small. 
         [0065]    The mass member  120  may have a mass required to induce the vibrations of the horizontal linear vibrator  100 . In other words, the mass of the mass member  120  may be changed depending on the natural vibrational frequency of the horizontal linear vibrator  100 . For example, when the natural vibrational frequency in a high frequency band is required, the mass of the mass member  120  may be decreased, and when the natural vibrational frequency in a low frequency band is required, the mass of the mass member  120  may be increased. 
         [0066]    The mass member  120  may be formed of a metal or a rubber material. The metal may be used in increasing a size of amass with a small size and the rubber material may be used in relieving a breakage phenomenon due to impact between the housing  110  and the mass member  120 . 
         [0067]    The magnet member  130  may be mounted in the mass member  120 . In other words, the magnet member  130  may be mounted on a circumference of the mass member  120  (see  FIG. 2 ). To this end, the circumference of the mass member  120  may be provided with a groove  122  in which the magnet member  130  is mounted. However, the circumference of the mass member  120  is not necessarily provided with the groove  122 . For example, the magnet member  130  may be attached to the circumference of the mass member  120  by an adhesive. 
         [0068]    Both ends (horizontal direction based on  FIG. 1 ) of the magnet member  130  may have different polarities. For example, one end of the magnet member  130  may be a first polarity (N pole) and the other end thereof may be a second polarity (S pole). The magnet member  130 , so disposed, may form a magnetic force, along with the coil member  140  to move the mass member  120  in a reciprocal manner in a length direction (horizontal direction based on  FIG. 1 ) of the housing  110 . 
         [0069]    As illustrated in  FIG. 1 , the magnet member  130  may be formed to be wider than the coil member  140 . The magnet member  130 , so formed, may continuously face the coil member  140  during the reciprocating motion of the mass member  120  to form the magnetic force. 
         [0070]    Meanwhile, as illustrated in  FIG. 3 , the magnet member  130  may be disposed to be deflected in one direction with respect to the coil member  140  in a state in which the mass member  120  stops. In other words, a center line C1-C1 of the magnet member  130  may be disposed to be deflected with a center line C2-C2 of the coil member  140  at a predetermined distance. The structure, so disposed, generates a magnetic field deflected in one direction between the magnet member  130  and the coil member  140 , which may be applied to the case of starting the mass member  120  in the stopped state. 
         [0071]    The coil member  140  may be mounted in the housing  110 . In other words, the coil member  140  may be mounted on an inner circumferential surface of the housing  110  and may be disposed at a position facing the magnet member  130  in the stop state of the mass member  120  (see  FIGS. 1 and 2 ). 
         [0072]    The coil member  140  may be connected to an external power supply. In other words, the coil member  140  may have a current applied thereto from the external power supply to generate a predetermined magnetic field. 
         [0073]    The so configured coil member  140  may alternately generate a magnetic field which coincides with or does not coincide with the magnetic field of the magnet member  130  depending on a supply direction of current, thereby reciprocally moving the mass member  120 . 
         [0074]    The elastic member  150  may be mounted in the receiving space  112  of the housing  110  and may provide a predetermined elastic force in a one-axis direction (horizontal direction based on  FIG. 1 ). To this end, the elastic member  150  may have a spring shape. In other words, the elastic member  150  may be a coil spring. 
         [0075]    The elastic member  150  may be disposed between one end of the housing  110  and one end of the mass member  120  and between the other end of the housing  110  and the other end of the mass member  120 . The elastic member  150 , so disposed, may provide elastic force in a direction opposite to a moving direction of the mass member  120 . For example, when the mass member  120  moves in a first direction (a left direction, based on  FIG. 1 ), the elastic member  150  may apply the elastic force to the mass member  120  in the second direction (a right direction, based on  FIG. 1 ), and when the mass member  120  moves in a second direction, the elastic member  150  may apply the elastic force to the mass member  120  in the first direction. 
         [0076]    Further, the elastic member  150  may prevent the mass member  120  from colliding with the housing  110 . In other words, the elastic member  150  may prevent both ends of the mass member  120  from colliding with left and right ends of the housing  110  due to a sudden motion of the mass member  120 . 
         [0077]    Meanwhile, the elastic members  150  disposed at both ends of the mass member  120  may have different elastic moduli as illustrated in  FIG. 3 . In other words, a first coil spring  152  disposed at one side of the mass member  120  may have a first spring constant and a second coil spring  154  disposed at the other side thereof may have a second spring constant. As such, when the coil springs  152  and  154  having different spring constants are disposed at both ends of the mass member  120 , deflecting the mass member  120  in one direction in the stop state of the mass member  120  may obtain the same as or a similar effect to deflecting the magnet member  130 . 
         [0078]    The bearing member  160  may be disposed between the housing  110  and the mass member  120  and may be mounted in the housing  110  or the mass member  120 . In other words, the bearing member  160  may be disposed between the inner circumferential surface of the housing  110  and an outer circumferential surface of the mass member  120 . The bearing member  160 , so disposed, relieves contact and friction between the inner circumferential surface of the housing  110  and the outer circumferential surface of the mass member  120 , thereby allowing for reciprocation of the mass member  120  to be smooth. 
         [0079]    According to the horizontal linear vibrator  100  configured as described above, the moving position of the mass member  120  may be stably maintained by the elastic member  150  and the bearing member  160  to stably secure straightness of the mass member  120 , thereby obtaining a constant and reliable vibrational frequency. Further, the horizontal linear vibrator  100  according to the embodiment of the present invention may prevent or relieve the collision phenomenon between the mass member  120  and the housing  110  due to the elastic member  150  and the bearing member  160 , thereby improving durability against external impact. 
         [0080]    Next, a horizontal linear vibrator according to another embodiment of the present invention will be described. For reference, in describing the following embodiments, components that are the same as those of the above-mentioned embodiment of the present invention will be denoted by the same reference numerals as the foregoing embodiments and a detailed description thereof will be omitted. 
         [0081]    Hereinafter, a horizontal linear vibrator according to a second embodiment of the present invention will be described with reference to  FIG. 4 . 
         [0082]    The horizontal linear vibrator  100  according to the embodiment of the present invention may be differentiated from the first embodiment in terms of the positions of the magnet member  130  and the coil member  140 . In other words, according to the embodiment of the present invention, the magnet member  130  may be mounted on the inner circumferential surface of the housing  110  and the coil member  140  may be mounted on the outer circumferential surface of the mass member  120 . 
         [0083]    The so configured horizontal linear vibrator  100  has a structure in which the coil member  140  is wound around the mass member  120  separable from the housing  110 , such that the coil member  140  may be mounted relatively easily. 
         [0084]    Next, a horizontal linear vibrator according to a third embodiment of the present invention will be described with reference  FIGS. 5 through 8 . 
         [0085]    The horizontal linear vibrator  100  according to the embodiment of the present invention may be differentiated from the foregoing embodiments in terms of the shapes of the housing  110  and the mass member  120 . In other words, according to the embodiment of the present invention, the housing  110  may be provided with the groove  114  and the mass member  120  may be provided with a protrusion  124 . 
         [0086]    The groove  114  may be formed lengthily in the length direction of the housing  110 . In other words, the groove  114  may be formed lengthily in the reciprocating motion direction (horizontal direction based on  FIG. 5 ) of the mass member  120 . 
         [0087]    The protrusion  124  may be formed in the mass member  120 . In other words, the protrusions  124  may be formed lengthily in the reciprocating motion direction of the mass member  120 . Alternatively, the plurality of protrusions  124  may be formed along the reciprocating motion direction of the mass member  120  at a predetermined distance. The protrusion  124  may be inserted into the groove  114  of the housing  110 . In other words, the protrusion  124  has a size which substantially coincides with the groove  114  and may move along the groove  114  in the significantly reduced contact friction state. That is, the protrusion  124  and the groove  114  are precisely machined with a significantly reduced tolerance, and therefore may slidably contact each other. 
         [0088]    According to the horizontal linear vibrator  100  configured as described above, the straightness of the mass member  120  may be secured by the protrusion  124  inserted into the groove  114 . Therefore, in the present embodiment, the bearing member  160  may be omitted, such that the manufacturing costs of the horizontal linear vibrator  100  may be saved and the manufacturing process thereof may be simplified. 
         [0089]    Meanwhile, as illustrated in  FIGS. 7 and 8 , the plurality of grooves  114  and the plurality of protrusions  124  may be formed in the circumference of the housing  110  and the mass member  120  at a predetermined distance. 
         [0090]    Next, a horizontal linear vibrator according to a fourth embodiment of the present invention will be described with reference  FIGS. 9 through 12 . 
         [0091]    The horizontal linear vibrator  100  according to the embodiment of the present invention may be differentiated from the foregoing embodiments in terms of the cross-sectional shapes of the housing  110  and the mass member  120 . 
         [0092]    In the present embodiment, the housing  110  may have a vertical or horizontal asymmetrical cross-sectional shape, a rectangular or squared cross-sectional shape, or a polygonal or oval cross-sectional shape. In other words, as illustrated in  FIG. 10 , the housing  110  may have a cross-sectional shape in which a portion of a circle is flat. Alternatively, as illustrated in  FIG. 11 , the housing  110  may have a rectangular cross-sectional shape. Alternatively, as illustrated in  FIG. 12 , the housing  110  may have an oval cross-sectional shape. That is, in the present embodiment, the housing  110  may have a cross-sectional shape having directivity. 
         [0093]    The mass member  120  may have a cross-sectional shape corresponding to the housing  110 . That is, the mass member  120  illustrated in  FIG. 10  may have the cross-sectional shape which coincides with a shape in which the housing  110  is reduced at a predetermined ratio, the mass member  120  illustrated in  FIG. 11  may have a rectangular or squared cross-sectional shape, and the mass member  120  illustrated in  FIG. 12  may have an oval cross-sectional shape. 
         [0094]    The cross-sectional shapes of the housing  110  and the mass member  120  having the above-mentioned shape have directivity, such that the mass member  120  may be deflected in a specific direction within the housing  110 . That is, the structure serves to restrict the motion of the mass member  120  in the section, thereby improving the straightness of the mass member  120 . 
         [0095]    As set forth above, according to the embodiments of the present invention, the high-frequency vibrations may be generated by forming the mass member to have an appropriate size. 
         [0096]    Further, according to the embodiments of the present invention, the manufacturing costs of the horizontal linear vibrator may be saved by significantly reducing the number of components of the horizontal linear vibrator. 
         [0097]    In addition, according to the embodiments of the present invention, since the internal structure of the horizontal linear vibrator is robust, an influence on the performance of the horizontal linear vibrator due to the external impact may be significantly reduced. 
         [0098]    While the present invention has been shown and described in connection with the 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.
There is provided a horizontal linear vibrator including a housing, a mass member movably mounted within the housing in a length direction thereof, a coil member mounted in the housing, a magnet member mounted in the mass member and interacting with the coil member to generate a magnetic field so as to enable movement of the mass member, an elastic member mounted in the housing and applying force in the same direction as or an opposite direction to a moving direction of the mass member, and a bearing member disposed between the mass member and the housing to enable a sliding motion of the mass member relative to the housing.