Abstract:
A vibration generating apparatus includes a mass body; an, elastic member coupled to the mass body; and a piezoelectric element disposed on one surface of the elastic member facing the mass body, wherein a surface of the mass body facing the piezoelectric element has a shape that prevents contact between the piezoelectric element and the mass body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a division of U.S. patent application Ser. No. 14/199,937, filed Mar. 6, 2014, which claimed benefit of U.S. Patent Application No. 61/803,602, filed on Mar. 20, 2013, and priority to Korean Patent Application No 10-2013-0137516, filed on Nov. 13, 2013, the disclosures of which are hereby incorporated by reference in their entireties herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Unless otherwise indicated herein, the materials described in this section are not prior art to the claims herein and are not admitted to be prior art by inclusion in this section. Embodiments of the present disclosure generally relate to a vibration generating apparatus. 
         [0004]    2. Description of Related Art 
         [0005]    A vibration generating apparatus converts electrical energy into mechanical vibrations using the principle of electromagnetic force. The vibration generating apparatus may be mounted in, for example, mobile phones, and the like, to thereby be used for silently notifying a user of call reception by transferring vibrations. In accordance with the rapid growth in the market for mobile devices such as the mobile phones, and the like, and with the trend for the addition of functionality to mobile devices, such mobile devices may be relatively small and have high quality. The demand for development of a vibration generating apparatus having a new structure capable of overcoming disadvantages of existing vibration generating apparatuses and quality has been improved. 
         [0006]    Further, as the release of smartphones, among other mobile phones has rapidly increased, a touchscreen scheme has been adopted for use therein, such that a vibration motor has been used in order to generate vibrations at the time a touchscreen is touched by a user. Examples of preferred performance of the vibrations associated with the touchscreen are as follows. First, since vibrations generated at the time a touchscreen is touched are generated frequently than vibrations generated at the time of call reception, an operational lifespan of a vibration generating apparatus may need to be increased. Second, in order to increase user satisfaction when a user feels vibrations when touching a touchscreen, a response speed of the vibrations may be increased in accordance with a touch speed of the touchscreen. 
         [0007]    For example, a piezo haptic actuator may be used Such a piezo haptic actuator may use a principle of an inverse piezoelectric effect in which displacement is generated when a voltage is applied to a piezo element, that is, a principle of allowing a weight of a mover to be moved by the generated displacement to generate vibrations. 
         [0008]    The vibrator may have the following exemplary features. A bandwidth of a frequency capable of obtaining a predetermined level of vibrational force or more may be wide, such that stable vibration characteristics may be implemented. Vibrations having low and high frequencies rather than a single frequency in a predetermined frequency range may be variously used. In addition, since the vibrator may implement rapid operational response characteristics, haptic vibrations may be implemented in a mobile device such as a mobile phone, or the like. 
       SUMMARY OF THE INVENTION 
       [0009]    Some embodiments of the present disclosure may provide a vibration generating apparatus capable of preventing damage to a piezoelectric element. 
         [0010]    According to some embodiments of the present disclosure, a vibration generating apparatus may include a vibration transferring member transferring vibrations to outside the vibration generating apparatus, an elastic member having one or more end portions fixed to the vibration transferring member, a mass body vibrating in response to vibrations of the elastic member, and a piezoelectric element installed on one surface of the elastic member so as to be disposed to face the mass body. A lower surface of the mass body may have step parts in order to prevent contact between the mass body and the piezoelectric element. The lower surface of the mass body in which the step parts are formed and the piezoelectric element may be disposed so as to be spaced apart from each other by a predetermined distance. 
         [0011]    The mass body may have an inclined surface formed on the lower surface thereof, wherein the inclined surface is inclined upwardly from the step part of the mass body toward a distal end thereof. 
         [0012]    The elastic member may include a bottom plate having both end portions fixed to the vibration transferring member. 
         [0013]    The bottom plate may have one or more openings formed therein in order to expose an electrode formed on the piezoelectric element. 
         [0014]    The bottom plate may have at least one elastic deformation assisting hole formed between the opening of the bottom plate and a distal end of the bottom plate so that elastic deformation of the bottom plate is facilitated. 
         [0015]    The openings and the elastic deformation assisting holes may be formed on both sides of the bottom plate so as to be symmetrical with regard to each other based on a center line of the bottom plate in a length direction thereof. 
         [0016]    The bottom plate may have at least one support protrusion formed thereon in order to provide an installation position for the piezoelectric element. 
         [0017]    The elastic member may further include extension plates extended from both side surfaces of a central portion of the bottom plate. 
         [0018]    The extension plates may include support plate parts contacting front and rear surfaces of the mass body, respectively, and connection parts coupling the support plate parts and the bottom plate to each other. 
         [0019]    The support plate parts may have one or more support jaws extended therefrom in order to support the lower surface of the mass body. The supporting jaws may be inserted into support jaw insertion grooves formed on the lower surface of the mass body. 
         [0020]    The vibration generating apparatus may further include a buffering member installed on the other surface of the elastic member so as to be disposed below the piezoelectric element. 
         [0021]    A lower case configuring the vibration transferring member may have at least one passage hole formed therein so that the buffering member passes therethrough when the elastic member vibrates. 
         [0022]    The lower case may have one or more protrusion parts formed thereon in order to support both end portions of the elastic member. 
         [0023]    The vibration generating apparatus may further include a circuit board connected to the piezoelectric element and installed on an upper surface of the elastic member. 
         [0024]    The elastic member may have an opening formed therein in order to expose an electrode formed on a lower surface of the piezoelectric element externally. The circuit board may be provided with an insertion hole, into which the electrode of the piezoelectric element is inserted, and be provided with a piezoelectric element connection part inserted into the opening. 
         [0025]    The circuit board may be provided with an external exposed part having power supply connection terminals formed thereon, disposed at one side of the piezoelectric element connection part, and bent. 
         [0026]    The vibration generating apparatus may further include a damage preventing member installed on at least one of an upper surface of the piezoelectric element and/or the lower surface of the mass body disposed so as to face the piezoelectric element and preventing damage to the piezoelectric element. 
         [0027]    The damage preventing member may be formed of a material having elasticity. 
         [0028]    The vibration transferring member may include a lower case having a plate shape and an upper case coupled to the lower case and having an internal space. 
         [0029]    The vibration generating apparatus may further include one or more damper members installed on an inner surface of the upper case, wherein the damper members are inserted into damper member insertion grooves formed on an upper surface of the mass body when the elastic member vibrates. 
         [0030]    The mass body may have a curved surface formed on the lower surface thereof, wherein the curved surface is curved from the step part of the mass body toward a distal end of the mass body. 
         [0031]    The curved surface may have a curvature equal to or larger than that of the elastic member in the state in which the elastic member is maximally deformed at the time of being deformed downwardly. 
         [0032]    According to some embodiments of the present disclosure, a vibration generating apparatus may include a vibration transferring member transferring vibrations to outside the vibration generating apparatus, an elastic member having one or more end portions fixed to the vibration transferring member, a mass body vibrating together with the elastic member when the elastic member vibrates, a piezoelectric element installed on one surface of the elastic member so as to be disposed to face the mass body, a circuit board connected to the piezoelectric element and installed on an upper surface of the elastic member, and a damage preventing member installed on at least one of an upper surface of the piezoelectric element or a lower surface of the mass body disposed so as to face the piezoelectric element and preventing damage to the piezoelectric element. The elastic member may have an opening formed therein in order to expose an electrode formed on a lower surface of the piezoelectric element. The circuit board may be provided with a piezoelectric element connection part inserted into the opening. The piezoelectric element may be disposed on the piezoelectric element connection part of the circuit board in the opening. 
         [0033]    The circuit board may be provided with an external exposed part having one or more power supply connection terminals formed thereon, disposed at one side of the piezoelectric element connection part, and bent. 
         [0034]    The damage preventing member may be formed of a material having elasticity. 
         [0035]    According to some embodiments of the present disclosure, a vibration generating apparatus may include a vibration transferring member transferring vibrations to outside of the vibration generating apparatus, an elastic member having one or more end portions fixed to the vibration transferring member, a mass body vibrating in response to vibrations of the elastic member when the elastic member vibrates, and a piezoelectric element installed on one surface of the elastic member. The elastic member may include a bottom plate having end portions fixed to the vibration transferring member. The bottom plate may have at least one support protrusion formed thereon in order to support both end portions and both side surfaces of the piezoelectric element. 
         [0036]    The bottom plate may have one or more openings formed therein in order to expose an electrode formed on the piezoelectric element. The number of support protrusions may be plural. At least two of support protrusions may be disposed at both end portions of the openings. 
         [0037]    According to some embodiments of the present disclosure, a vibration generating apparatus may include a vibration transferring member transferring vibrations to outside the vibration generating apparatus, an elastic member having one or more end portions fixed to the vibration transferring member, a mass body vibrating in response to vibrations of the elastic member, and a piezoelectric element installed on one surface of the elastic member so as to be disposed to face the mass body. 
         [0038]    According to some embodiments of the present disclosure, a vibration generating apparatus may include a vibration transferring member transferring vibrations externally, an elastic member having one or more end portions fixed to the vibration transferring member, a mass body vibrating in response to vibrations of the elastic member, and piezoelectric elements installed on both surfaces of the elastic member, any one of the piezoelectric elements being disposed so as to face the mass body. The mass body may have one or more step parts formed in a lower surface thereof in order to prevent contact between the mass body and the piezoelectric element. The lower surface of the mass body in which the step parts are formed and the piezoelectric element may be disposed so as to be spaced apart from each other by a predetermined distance. 
         [0039]    According to some embodiments, a vibration generating apparatus may comprise amass body, an elastic member coupled to the mass body, and a piezoelectric element disposed on one surface of the elastic member facing the mass body. A surface of the mass body facing the piezoelectric element may have a shape that prevents contact between the piezoelectric element and the mass body. 
         [0040]    The surface of the mass body may have one or more stepped parts formed to correspond to the piezoelectric element. 
         [0041]    The surface of the mass body may comprise an inclined surface from the stepped part toward a distal end of the mass body. 
         [0042]    The elastic member may comprise a bottom plate, and support plate parts extending vertically from the bottom plate and supporting the mass body. The piezoelectric element may be installed on a surface of the bottom plate facing the mass body. 
         [0043]    The vibration generating apparatus further comprise a case transferring vibrations to outside the vibration generating apparatus and coupled with the elastic member. 
         [0044]    The vibration generating apparatus may further comprise one or more damper members attached on an inner surface of the case. 
         [0045]    The vibration generating apparatus may further comprise one or more damage preventing members disposed on a surface of the piezoelectric element facing the mass body. 
         [0046]    The vibration generating apparatus may further comprise one or more buffering members attached on another surface of the elastic member. 
         [0047]    The case may have at least one opening through which the buffering members are moveable. 
         [0048]    An inner surface of the ease may comprise one or more protrusions supporting end portions of the elastic member. 
         [0049]    The vibration generating apparatus may further comprise a circuit board connected to the piezoelectric element and disposed on the one surface of the elastic member. 
         [0050]    The electric member may comprise one or more openings exposing an electrode formed on a surface of the piezoelectric element. The circuit board may comprise an insertion hole, into which the electrode is inserted, and a piezoelectric element connection part inserted into the openings. 
         [0051]    The circuit board may comprise an external part extended to outside of the case and having a power supply connection terminal. 
         [0052]    The elastic member may have one or more holes. 
         [0053]    The surface of the mass body may comprise a curved surface between the stepped part and a distal end of the mass body. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0054]    Embodiments of the present disclosure will be more clearly understood from the following description taken in conjunction with the accompanying drawings, in which: 
           [0055]      FIG. 1  is a schematic cross-sectional view showing a vibration generating apparatus according to an exemplary embodiment of the present disclosure; 
           [0056]      FIG. 2  is an exploded perspective view showing the vibration generating apparatus according to an exemplary embodiment of the present disclosure; 
           [0057]      FIG. 3  is a perspective view showing an upper case included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure; 
           [0058]      FIG. 4  is a perspective view showing a lowercase included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure, 
           [0059]      FIG. 5  is a plan view showing an elastic member included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure, 
           [0060]      FIG. 6  is a perspective view showing the elastic member included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure; 
           [0061]      FIG. 7  is a bottom perspective view showing a piezoelectric element included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure; 
           [0062]      FIG. 8  is a perspective view showing amass body included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure; 
           [0063]      FIG. 9  is a perspective view showing a circuit board included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure; and 
           [0064]      FIG. 10  is a schematic cross-sectional view showing a vibration generating apparatus according to another exemplary embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0065]    Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The disclosure 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 to explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. In the drawings, the shapes and dimensions of elements may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like elements. It will also be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. As used in this description and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
         [0066]      FIG. 1  is a schematic cross-sectional view showing a vibration generating apparatus according to an exemplary embodiment of the present disclosure.  FIG. 2  is an exploded perspective view showing the vibration generating apparatus according to an exemplary embodiment of the present disclosure. 
         [0067]    Referring to  FIGS. 1 and 2 , a vibration generating apparatus  100  according to an exemplary embodiment of the present disclosure may include a vibration transferring member  120 , an elastic member  140 , a piezoelectric element  160 , a mass body  180 , a circuit board  200 , a buffering member  220 , a damper member  240 , and a damage preventing member  260  by way of example. 
         [0068]    Terms with respect to directions are defined below. As viewed in  FIG. 3 , a length direction refers to an X direction and a width direction refers to a Y direction. In addition, a height direction refers to a Z direction. The terms defined above are used below, having the same meaning as the defined meaning. That is, in describing the respective components, the terms described above indicate the same directions as the defined directions. 
         [0069]    The vibration transferring member  120  may be configured to transfer vibrations externally and may have, for example, but not limited to, a rectangular parallelepiped shape. In addition, the vibration transferring member  120  may include an upper case  122  and a lower case  130 . For example, the upper case  122  may have a box shape which has an internal space, and the lower case  130  may have a plate shape. 
         [0070]      FIG. 3  is a perspective view showing an upper case included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure. 
         [0071]    Referring to  FIGS. 1 through 3 , the upper case  122  of the vibration transferring member  120  may have a box shape, but a lower portion of the upper case  122  may be opened. The upper case  122  may include a front plate  123 , side plates  124  and  125 , a rear plate  126 , and an upper plate  127 . The height of at least one of side plates  124  and  125  may be shorter than that of the front plate  123  and the rear plate  126  in a height direction to form an opening. 
         [0072]    The circuit board  200  may be exposed outside the vibration transferring member  120  through the opening formed at an end portion of the upper case  122 . 
         [0073]    The front plate  123  and/or the rear plate  126  may have a single or a plurality of grooves  129  formed therein in order to allow the upper case  122  to be fixedly coupled to the lower case  130 . 
         [0074]    The upper plate  126  may have vent holes  128  formed therein in order to allow air to flow to an inner portion or an outer portion of the vibration transferring member  120  when the elastic member  140  vibrates. 
         [0075]      FIG. 4  is a perspective view showing a lower case included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure. 
         [0076]    Referring to  FIGS. 1 through 4 , the lower case  130  may have a plate shape. The lower case  130  may have protrusion parts  132  formed on or near both end portions thereof, respectively, in order to support both end portions of the elastic member  140 . For instance, the protrusion part  132  may be formed by indenting and have a rectangular pillar shape. 
         [0077]    At least one of both end portions of the lower case  130  may be provided with an extension plate  133  extended so as to protrude from the upper case  122  in the length direction thereof. The extension plate  133  may provide a seating surface for an exposed portion of the circuit board  200 . 
         [0078]    In addition, the lower case  130  may have a passage hole  134  formed in a central portion thereof so that the buffering member  220  may pass therethrough. The passage hole  134  may serve as a movement path through which the buffering member  220  installed on the elastic member  140  descends downwardly of the lower case  130  when the elastic member  140  vibrates. Therefore, a displacement amount of the elastic member  140  may be increased. 
         [0079]    In addition, the passage hole  134  may have various shapes depending on a shape of the buffering member  220 . 
         [0080]    The lower case  130  may have coupling wall parts  136  formed in order to increase coupling force between the lower case  130  and the upper case  122 . Outer surfaces of the coupling wall parts  136  may contact inner surfaces of the front plate  123  and the rear plate  126  to be configured to increase contact area between the upper case  122  and the lower case  130  when the upper case  122  and the lower case  130  are coupled to each other. 
         [0081]    In addition, the lower case  130  may have grooves  138  formed therein so as to correspond to the plurality of grooves  129  formed in the upper case  122 . The grooves  138  of the lower case  130  and the grooves  129  of the upper case  122 , which are to facilitate assembling between the lower case  130  and the upper case  122 , may not be formed in the lower case  130  and the upper case  122 . 
         [0082]      FIG. 5  is a plan view showing an elastic member included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure.  FIG. 6  is a perspective view showing the elastic member included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure. 
         [0083]    Referring to  FIGS. 1 through 6 , the elastic member  140  may have end portions fixed to the vibration transferring member  120 . For example, the elastic member  140  may be fixed to the protrusion parts  132  of the lower case  130 . Therefore, the elastic member  140  may have fixed ends at both end portions thereof, respectively. Although the elastic member  140  is fixed to the lower case  130  by way of example in an exemplary embodiment of the present disclosure, the present disclosure is not limited thereto. The elastic member  140  may be installed in the upper case  122 . 
         [0084]    In addition, the elastic member  140  may be installed in the vibration transferring member  120  so that both end portions of the elastic member  140  are interposed between the upper case  122  and the lower case  130 . 
         [0085]    The elastic member  140  may include a bottom plate  142  and extension plates  144 , as shown in  FIGS. 5 and 6 . The bottom plate  142  may include a plurality of support protrusions  142   a  and  142   b  for installing the piezoelectric element  160  on the elastic member  140 . 
         [0086]    Two support protrusions  142   a  may support both side surfaces of the piezoelectric element  160 , and the other support protrusions  142   b  may support other two side surfaces (front and rear surfaces) of the piezoelectric element  160 .  160 . 
         [0087]    Therefore, the piezoelectric element  160  may be installed at a predetermined position, and coupling force between the bottom plate  142  and the piezoelectric element  160  may be increased to facilitate elastic deformation of the bottom plate  142  at the time of deformation of the piezoelectric element  160 . 
         [0088]    Further, the coupling force between the bottom plate  142  and the piezoelectric element  160  may be increased by the support protrusions  142   a  and  142   b  to prevent the piezoelectric element  160  from being separated from the bottom plate  142 . 
         [0089]    In addition, the support protrusions  142   a  and  142   b  may serve to amplify a deformation amount of the piezoelectric element  160  at the time of the deformation of the piezoelectric element  160 . For example, the support protrusions  142   a  and  142   b  may support both end portions and both side surfaces of the piezoelectric element  160 , thereby increasing efficiency in transferring a deformation amount to the bottom plate  142  at the time of the deformation of the piezoelectric element  160 . 
         [0090]    The bottom plate  142  may have openings  142   c  formed therein in order to electrically connect the circuit board  200  and the piezoelectric element  160  to each other. The openings  142   c  may be formed in the bottom plate  142  so that both end portions of a lower surface of the piezoelectric element  160  may be exposed at the time of installing the piezoelectric element  160 . That is, at the time of installing the piezoelectric element  160 , a central portion of the lower surface of the piezoelectric element  160  may be supported by the bottom plate  142 , and both end portions of the lower surface of the piezoelectric element  160  may be exposed to the opening  142   c.    
         [0091]    A single or a plurality of elastic deformation assisting holes  142   d  may be formed between the openings  142   c  and end portions of the bottom plate  142  in order to decease rigidity of the bottom plate  142  so that elastic deformation of the bottom plate  142  is facilitated. That is, the number of elastic deformation assisting holes  142   d , holes formed in order to facilitate elastic deformation of regions adjacent to both end portions of the bottom plate  142 , may be provided in plural, and have various shapes. 
         [0092]    The bottom plate  142  may have support parts  142   e  formed at both end portions thereof, respectively. The support parts  142  may be supported by the protrusion parts  132  of the lower case  130 , respectively. 
         [0093]    The extension plates  144  may include support plate parts  146  contacting a front surface and a rear surface of the mass body  180 , respectively, and connection parts  148  connecting the support plate parts  146  and the bottom plate  142  to each other, respectively, and/or supporting the mass body  180  as shown in  FIG. 6 . 
         [0094]    The connection parts  148  may be extended from front and rear surfaces of the bottom plate  142 , respectively. In addition, the connection part  148  may include first and second connection parts  148   a  and  148   b  disposed so as to be spaced apart from each other by a predetermined distance in the length direction. 
         [0095]    The connection part  148  may include the first and second connection parts  148   a  and  148   b , such that the support plate part  146  and the bottom plate  142  may be more firmly connected to each other. 
         [0096]    The support plate parts  146  may be extended in a length direction of the mass body  180  and may have inner surfaces contacting the front and rear surface of the mass body  180 , respectively and or supporting the mass body  180 . For example, the support plate part  146  may have a length equal to or longer than that of the mass body  180 . The support plate part  146  may have a shape approximately corresponding to that of the mass body  180 . 
         [0097]    The support plate part  146  may be provided with support jaws  146   a  for supporting a lower surface of the mass body  180 . The support jaws  146   a  may be disposed so as to be spaced apart from each other by a predetermined distance in a length direction of the support plate part  146 . For example, the support jaws  146   a  may be disposed so as to be adjacent to both end portions of the mass body  180 , respectively. 
         [0098]    A position of the mass body  180  in a height direction may be controlled by the support jaws  146   a . For example, the mass body  180  may be disposed so as to be spaced apart from the bottom plate  142  of the elastic member  140  by a predetermined distance by the support jaws  146   a.    
         [0099]      FIG. 7  is a bottom perspective view showing a piezoelectric element included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure. 
         [0100]    Referring to  FIGS. 1 through 7 , the piezoelectric element  160  may be installed on one surface of the elastic member  140  so as to be disposed to face the mass body  180 . For example, the piezoelectric element  160  may be fixedly installed on an upper surface of the bottom plate  142  so as to be disposed between the lower surface of the mass body  180  and the bottom plate  142  of the elastic member  140 . 
         [0101]    The piezoelectric element  160  may have, for example, but not limited to, a rectangular parallelepiped shape as shown in  FIG. 7 . One end portion of the lower surface of the piezoelectric element  160  may be provided with an electrode  162 . The electrode  162  may protrude from the lower surface of the piezoelectric element  160  and have a positive (+) electrode  162   a  and a negative (−) electrode  162   b.    
         [0102]    In the case in which the piezoelectric element  160  is installed on the bottom plate  142  of the elastic member  140 , both side surfaces of the piezoelectric element  160  may be supported by two first support protrusions  142   a , and the front and rear surfaces of the piezoelectric element  160  may be supported by two support protrusions  142   b.    
         [0103]    In addition, in the case in which the piezoelectric element  160  is installed on the bottom plate  142 , the electrode  162  described above may be inserted into the opening  142   c  of the bottom plate  142 . 
         [0104]    Further, in the case in which the piezoelectric element  160  is installed on the bottom plate  142 , the piezoelectric element  160  may be disposed so as to be spaced apart from the lower surface of the mass body  180  by a predetermined distance. 
         [0105]      FIG. 8  is a perspective view showing a mass body included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure. 
         [0106]    Referring to  FIGS. 1 through 8 , the mass body  180  may vibrate together with the elastic member  140  when the elastic member  140  vibrates. The mass body  180  may have, for instance, a bar shape, and may have step parts  182  formed on a lower surface thereof in order to prevent contact between the mass body  180  and the piezoelectric element  160 . 
         [0107]    In addition, the lower surface of the mass body  180  on which the step parts  182  are formed may be disposed so as to be spaced apart from the piezoelectric element  160  by a predetermined distance. The mass body  180  may be provided with the step parts  182  in order to prevent contact between the piezoelectric element  160  and the mass body  180  when the bottom plate  142  of the elastic member  140  is elastically deformed in response to expansion and contraction of the piezoelectric element  160 . Therefore, even at the time of elastic deformation of the bottom plate  142 , the piezoelectric element  160  and the mass body  180  may not contact each other. 
         [0108]    The step part  182  may have a single or a plurality of steps. 
         [0109]    The mass body  180  may have stopper parts  184  formed at both end portions of the lower surface thereof in order to limit displacement of the mass body  180  at the time of the elastic deformation of the elastic member  140 . That is, the stopper parts  184  may contact the end portions of the bottom plate  142  of the elastic member  140  to limit the displacement of the mass body  180 . Therefore, contact between the mass body  180  and the bottom plate  142  in inner regions of both end portions of the bottom plate  142  may be prevented. 
         [0110]    For example, the stopper parts  184  may contact the end portions of the bottom plate  142  of the elastic member  140  at the time of the elastic deformation of the elastic member  140  or at the time external impacts applied to the vibration generating apparatus, such that the mass body  180  cannot descend downwardly below a predetermined level. Therefore, contact between the mass body  180  and the piezoelectric element  160  may be prevented. 
         [0111]    Support jaw insertion grooves  186  may be formed on the mass body  180  so as to be disposed between the stopper parts  184  and the step parts  182  of the mass body  180 , respectively. The mass body  180  may be installed on the elastic member  160  so that the support jaws  146   a  of the elastic member  140  are inserted into the support jaw insertion grooves  186 , respectively. In addition, the position of the mass body  180  in the height direction may be controlled by the support jaws  146   a.    
         [0112]    Further, the mass body  180  may have an inclined surface  188  formed from the step part  182  thereof on the lower surface thereof. The inclined surface  188  may have a gradient so as to prevent contact with the bottom plate  142  at the time of the elastic deformation of the elastic member  140 . For example, the inclined surface  188  may have a gradient equal to or smaller than that of an absolute value of the bottom plate  142  in a shape in which the bottom plate  142  is maximally deformed at the time of being elastically deformed. 
         [0113]    Although the case in which the inclined surface  188  is inclined is shown in  FIG. 8  and described by way of example in an exemplary embodiment of the present disclosure, the present disclosure is not limited thereto. For example, the mass body  180  may have a curved surface formed on the lower surface thereof. The curved surface is curved from the step part  182  of the mass body  180  toward a distal end thereof. 
         [0114]    The curved surface may have a curvature equal to or larger than that of the elastic member  140  in the state in which the elastic member  140  is maximally deformed at the time of being deformed downwardly. 
         [0115]    Further, the mass body  180  may have damper member insertion grooves  190  formed on an upper surface thereof. The damper member insertion grooves  190  may be disposed below the damper members  240  and have the damper members  240  inserted thereinto when the elastic member  140  vibrates. 
         [0116]      FIG. 9  is a perspective view showing a circuit board included in the vibration generating apparatus according to an exemplary embodiment of the present disclosure. 
         [0117]    Referring to  FIGS. 2 and 9 , the circuit board  200  may be connected to the piezoelectric element  160  and vibrate together with the elastic member  140 . The circuit board  200  may be provided with a piezoelectric element connection part  202 . The piezoelectric element connection part  202  may have insertion holes  204  into which the electrodes  162  of the piezoelectric element  160  are inserted. 
         [0118]    The piezoelectric element connection part  202  may be inserted into the opening  142   c  shown in  FIG. 5  formed in the bottom plate  142  of the elastic member  140 . 
         [0119]    Therefore, a solder for connecting the piezoelectric element  160  and the circuit board  200  to each other may be disposed in the opening  142   c  of the bottom plate  142 , such that an increase in a thickness due to the solder may be suppressed. 
         [0120]    The piezoelectric element connection part  202  may be formed to be stepped with respect to a body  206  of the circuit board  200 . The piezoelectric element connection part  202  and the body  206  may be connected to each other by an inclined part  205 . 
         [0121]    The inclined part  205  may be provided with a support protrusion insertion hole  205   a  into which the support protrusion  142   a  shown in  FIG. 5  of the bottom plate  142  is inserted. 
         [0122]    The body  206  may have a plurality of holes and/or grooves formed therein so as to smoothly vibrate together with the bottom plate  142 . 
         [0123]    The circuit board  200  may be provided with an external exposed part  208  having power supply connection terminals  208   a  formed thereon and exposed outside the upper case  122 . The external exposed part  208  may be formed to be stepped with respect to the body  206 . 
         [0124]    A scheme of assembling the circuit board  200  is schematically described. The circuit board  200  may be installed on the upper surface of the bottom plate  142  of the elastic, member  140 . For example, the body  206  may be installed on the upper surface of the bottom plate  142 , and the inclined part  205  and the piezoelectric element connection part  202  extended from one end of the body  206  may be inserted into the opening  142   c  formed in the bottom plate  142 . 
         [0125]    Here, the inclined part  205  and the piezoelectric element connection part  202  may be disposed at a predetermined position by the support protrusion  142   a  of the bottom plate  142 . The piezoelectric element connection part  202  inserted into the opening  142   c  may be disposed below the piezoelectric element  160 . 
         [0126]    The external exposed part  208  extended from the other end of the body  206  may be exposed outside the upper case  122  through the opening disposed below the side plate  125  of the upper case  122 . 
         [0127]    The external exposed part  208  may be seated on the extension plate  133  of the lower case  130 . 
         [0128]    Referring to  FIGS. 1 and 2 , the buffering member  220  may be fixedly installed on the lower surface of the elastic member  140 . For instance, the buffering member  220  may be installed on a lower surface of the bottom plate  142  of the elastic member  140  to thereby vibrate together with the bottom plate  142 . 
         [0129]    The buffering member  220  may descend downwardly of the lower case  130  while passing through the lower case  130  via the passage hole  134  formed in the lower case  130  when the elastic member  140  vibrates. 
         [0130]    The buffering member  220  may not be subjected to interference of vibrations by the lower case  130 , such that a displacement amount of the elastic member  140  may be increased. 
         [0131]    The damper member  240  may be fixedly installed on a lower surface of the upper plate  126  of the case  122  and be disposed on the damper member insertion groove  190  of the mass body  180 . The damper member  240  may, for example, decrease noise generated due to contact between the mass body  180  and the upper case  122  and prevent damage to the upper case  122  and/or the mass body  180 . 
         [0132]    The damage preventing member  260  may be installed on an upper surface of the piezoelectric element  160  to prevent damage to the piezoelectric element  160 . For example, the damage preventing member  260  may be formed of a tape attached to the upper surface of the piezoelectric element  160 . 
         [0133]    The buffering member  220 , the damper member  240 , and/or the damage preventing member  260  described above may not be included in the vibration generating apparatus  100 . 
         [0134]    For instance, since the piezoelectric element  160  may be installed on the upper surface of the bottom plate  142  of the elastic member  140 , damage to the piezoelectric element  160  may be prevented when external impacts are applied to the vibration generating apparatus. Further, since contact between the piezoelectric element  160  and the lower case  130  may be prevented, generation of noise may be decreased. Additionally, space utilization of a lower region in an internal space of the vibration transferring member  120  divided by the elastic member  140  may be improved. The vibration generating apparatus  100  may be further thinned. 
         [0135]    As the piezoelectric element connection part  202  of the circuit board  200  is installed into the opening  142   c  formed in the bottom plate  142  of the elastic member  140 , an increase in a thickness due to the solder for connecting the circuit board  200  and the piezoelectric element  160  to each other may be prevented. 
         [0136]    In addition, since the buffering member  220  may descend downwardly of the lower case  130  by passing the passage hole  134  of the lower case  130 , thinness of the vibration generating apparatus  100  may be implemented. 
         [0137]    As described above, the piezoelectric element  160  may be installed on the upper surface of the elastic member  140 , such that the piezoelectric element  160  and the lower case  130  may not contact each other when the external impacts are applied to the vibration generating apparatus, whereby the damage to the piezoelectric element  160  may be prevented. 
         [0138]    In addition, the step part  182  for preventing contact between the mass body  180  and the piezoelectric element  160  may be formed in the mass body  180 , whereby the damage to the piezoelectric element  160  may be prevented. 
         [0139]    Further, the inclined surface  188  having a gradient corresponding to a shape of the elastic member  140  when the elastic member  140  is maximally deformed may be formed on the lower surface of the mass body  180 , whereby the generation of the noise due to the contact between the mass body  180  and the elastic member  140  may be prevented. 
         [0140]    Further, the efficiency in transferring the deformation amount at the time of the deformation of the piezoelectric element  160  may be increased by the support protrusions  142   a  and  142   b  of the elastic member  140 , and the coupling force between the piezoelectric element  160  and the elastic member  140  may be increased by the support protrusions  142   a  and  142   b  of the elastic member  140 . 
         [0141]    Hereinafter, a vibration generating apparatus according to another exemplary embodiment of the present disclosure will be described with reference to the accompanying drawings. However, a detailed description of the same components as the above-mentioned components will be omitted and be replaced by the above-mentioned description. 
         [0142]      FIG. 10  is a schematic cross-sectional view showing a vibration generating apparatus according to another exemplary embodiment of the present disclosure. 
         [0143]    Referring to  FIG. 10 , a vibration generating apparatus  300  according to another exemplary embodiment of the present disclosure may include a vibration transferring member  120 , an elastic member  140 , piezoelectric elements  360 , a mass body  180 , a circuit board  200 , a buffering member  220 , a damper member  240 , and a damage preventing member  260  by way of example. 
         [0144]    Since the vibration transferring member  120 , the elastic member  140 , the mass body  180 , the circuit board  200 , the buffering member  220 , the damper member  240 , and the damage preventing member  260  are the same as or similar with those of the vibration generating apparatus  100  according to an exemplary embodiment of the present disclosure described above, a detailed description thereof is omitted. 
         [0145]    The piezoelectric elements  360  may be installed on both surfaces of the elastic member  140 , and one of the piezoelectric elements  360  may be disposed so as to face the mass body  180 . For example, the piezoelectric elements  360  may include a first piezoelectric element  362  installed on one surface of the elastic member  140  and a second piezoelectric element  364  installed on the other surface of the elastic member  140 . 
         [0146]    As described above, the piezoelectric elements  360  may include the first and second piezoelectric elements  362  and  364  installed on both surfaces of the elastic member  140 , whereby a vibration amount may be increased. 
         [0147]    The buffering member  220  may be fixedly installed on the second piezoelectric element  364  formed on the other surface of the elastic member  140 . 
         [0148]    The piezoelectric element  360  may be installed on the upper surface of the elastic member  140 , such that the piezoelectric element  360  and the lower case  130  may not contact each other at the time of applying the external impact to the vibration generating apparatus, whereby the damage to the piezoelectric element  360  may be prevented. 
         [0149]    In addition, the step part  182  for preventing the contact between the mass body  180  and the piezoelectric element  360  is formed on the mass body  180 , whereby the damage to the piezoelectric element  360  may be prevented. 
         [0150]    Further, the inclined surface  188  having the gradient corresponding to a shape of the elastic member  140  when the elastic member  140  is maximally deformed is formed on the lower surface of the mass body  180 , whereby the generation of the noise due to the contact between the mass body  180  and the elastic member  140  may be prevented. 
         [0151]    While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the spirit and scope of the present disclosure as defined by the appended claims. Accordingly, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed.