Abstract:
Disclosed herein is a piezoelectric vibration module including a vibration plate that is surrounded by an upper case and a lower case, and includes a stopper capable of preventing direct collision between a piezoelectric element and an internal constituent member, for example, a lower case while vibrating linearly therein.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2012-0048712, filed on May 8, 2012, entitled “Piezoelectric Vibration Module”, which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a piezoelectric vibration module. 
         [0004]    2. Description of the Related Art In general, in portable electronic apparatuses such as a cellular phone, an electronic book (E-book) terminal, a game machine, a PMP, and the like, a vibration function is used for various purposes. 
         [0005]    In particular, a vibration generator for generating vibration is primarily mounted on the portable electronic apparatuses to be used as a warning function which is a silent receiving signal. 
         [0006]    Due to implementation of multi-functions of the portable electronic apparatuses, the vibration generator actually requires miniaturization, integration, and various high-functionality at present. 
         [0007]    Furthermore, a touch type device has been generally adopted, which performs an input operation by touching the portable electronic apparatus according to a user&#39;s request to intend to conveniently use the portable electronic apparatus. 
         [0008]    A haptic device which is currently in common use widely includes even a concept of reflecting interface user&#39;s intuitive experience and further diversifying a feedback for a touch in addition to a concept of performing an input operation through the touch. The haptic device generally provides vibration through repeated extension and/or shrinkage as external power is applied to a piezoelectric element. The piezoelectric element can improve moisture-resistance and durability as disclosed in an ultrasonic linear motor of Patent Document 1. 
         [0009]    In the ultrasonic linear motor according to Patent Document 1, a protection material, for example, silicon rubber surrounds the circumference of the piezoelectric element to prevent collision with a plurality of constituent members constituting the ultrasonic linear motor so as to improve the life-span thereof as well as the performance of the piezoelectric element under an environment with high humidity or an environment with lots of dust. 
         [0010]    However, the ultrasonic linear motor according to Patent Document 1 surrounds the rest of the parts other than a part of the piezoelectric element generating vibration force through translation movement, and as a result, extension or shrinkage deformation rate is remarkably reduced. 
         [0011]    That is, the protection material in the related art may still cause the vibration force of the piezoelectric element from deteriorating. Therefore, another measure for protecting the piezoelectric element from external factors should be taken. 
       PRIOR ART DOCUMENT 
     Patent Document 
       [0000]    
       
         (Patent Document 1) Patent Document 1: Japanese U.M. Laid-Open Publication No. Hei 2-94486 
       
     
       SUMMARY OF THE INVENTION 
       [0013]    The present invention has been made in an effort to provide a piezoelectric vibration module that can prevent direct collision with internal constituent members due to external shock of a piezoelectric element and/or unexpected large driving variation of the piezoelectric element when the piezoelectric element is activated. 
         [0014]    According to a first preferred embodiment of the present invention, there is provided a piezoelectric vibration module, including: a piezoelectric element generating vibration force through repetition of extension and shrinkage deformation by applying external power; an upper case having a bottom surface opened and an inner space formed therein so that the piezoelectric element vibrates linearly; a lower case coupled to the bottom surface of the upper case and shielding the inner space of the upper case; and a vibration plate including a lower plate mounted with the piezoelectric element and a stopper extending vertically downward at an edge of the lower plate, and placed in the upper case and the lower case and driven vertically. 
         [0015]    The vibration plate may include: the lower plate; a pair of upper plates that stand vertically at the centers of both sides of the lower plate; and a weight body placed between the pair of upper plates in order to increase the vibration force of the piezoelectric element. 
         [0016]    The lower case and the lower plate may be spaced apart from each other with a predetermined gap therebetween. 
         [0017]    The length of the stopper may be shorter than a spaced distance between the lower case and the lower plate and the stopper may extend more than the thickness of the piezoelectric element. 
         [0018]    The stopper may be made of the same material as the lower plate. 
         [0019]    The stopper may be made of a rigid material. 
         [0020]    The stopper may be arranged at the edge to be symmetric around the center of the lower plate. 
         [0021]    The stopper may be provided at one edge of two edges that are arranged in parallel with each other in a longitudinal direction of the lower plate or at both edges. 
         [0022]    The stopper may be placed to be adjacent to both ends of the lower plate. 
         [0023]    According to a second preferred embodiment of the present invention, there is provided a piezoelectric vibration module, including: a piezoelectric element generating vibration force through repetition of extension and shrinkage deformation by applying external power; an upper case having a bottom surface opened and an inner space formed therein so that the piezoelectric element vibrates linearly; a lower case coupled to the bottom surface of the upper case and shielding the inner space of the upper case; and a vibration plate including a lower plate mounted with the piezoelectric element and a stopper extending vertically downward at an edge of the lower plate and placed in the upper case and the lower case and driven vertically. 
         [0024]    The vibration plate may include: the lower plate; a pair of upper plates that stand vertically at the centers of both sides of the lower plate; and a weight body placed between the pair of upper plates in order to increase the vibration force of the piezoelectric element. 
         [0025]    The lower case and the lower plate may be spaced apart from each other with a predetermined gap therebetween. 
         [0026]    The length of the stopper may be shorter than a spaced distance between the lower case and the lower plate and the stopper may extend more than the thickness of the piezoelectric element. 
         [0027]    The stopper may be made of the same material as the lower plate. 
         [0028]    The stopper may be made of a rigid material. 
         [0029]    The stopper may be provided at one edge of two edges that are arranged in parallel with each other in a longitudinal direction of the lower plate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    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: 
           [0031]      FIG. 1  is a perspective view of a piezoelectric vibration module according to a first preferred embodiment of the present invention; 
           [0032]      FIG. 2  is an exploded perspective view of the piezoelectric vibration module illustrated in  FIG. 1 ; 
           [0033]      FIG. 3  is a front view schematically illustrating the piezoelectric vibration module according to the first preferred embodiment of the present invention except for an upper case; 
           [0034]      FIGS. 4A and 4C  are diagram illustrating a driving process of the piezoelectric vibration module illustrated in  FIG. 3 ; and 
           [0035]      FIG. 5  is a diagram schematically illustrating a piezoelectric vibration module according to a second preferred embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    The objects, features and advantages of the present invention will be more clearly understood from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted. Further, in the following description, the terms “first”, “second”, “one side”, “the other side” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. Further, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted. 
         [0037]    Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
         [0038]      FIG. 1  is a perspective view of a piezoelectric vibration module according to a first preferred embodiment of the present invention.  FIG. 2  is an exploded perspective view of the piezoelectric vibration module illustrated in  FIG. 1 . 
         [0039]    As illustrated in the figures, the piezoelectric vibration module  100  according to the first preferred embodiment of the present invention includes an upper case  110 , a vibration plate  120 , a weight body  130 , and a lower case  140 . The piezoelectric vibration module  100  is used as a means for transferring vibration force to a touch screen panel (not illustrated). 
         [0040]    The upper case  100  has a box shape in which one surface is opened and receives a driving body, that is, the vibration plate  120  mounted with a piezoelectric element  123 . 
         [0041]    The vibration plate  120  transfers vibration force of the piezoelectric element  123  to external components by a bending operation through repetition of extension and shrinkage transformation integrally with the piezoelectric element  123  as described above and includes a generally flat lower plate  121 . The piezoelectric element  130  is mounted on one flat surface of the lower plate  121  and the weight body  130  is mounted or placed on the other surface of the lower plate  121 . The vibration plate  120  may include a printed circuit board (PCB) (not illustrated) that applies power for driving the piezoelectric element  123 . 
         [0042]    Alternatively, the vibration plate  120  may include a pair of upper plates  122  that stand vertically upward on both sides of the lower plate  121  together with the flat lower plate  121  as described above. The upper plate  122  is coupled to the center of the lower plate  121 . Each of the lower plate  121  and the upper plate  121  may be formed by a single integral component and may be fixedly coupled by various bonding methods unlike the above. 
         [0043]    The vibration plate  120  is made of a metallic material having elastic force, for example, SUS to be transformed integrally with the piezoelectric element  123  which repeatedly extends or shrinks according to application of external power. When the vibration plate  120  and the piezoelectric element  123  are coupled to each other by the bonding coupling method, the vibration plate  120  may be made of invar which is a material having a similar thermal expansion coefficient as the piezoelectric element so as to prevent a bending phenomenon which may occur by hardening of a bonding member. 
         [0044]    As described above, the vibration plate  120  is made of invar having the similar thermal expansion coefficient as the piezoelectric element  123 , such that thermal stress is reduced, which is generated when the piezoelectric element  123  operates or is subjected to thermal shock even under a high-temperature external environment, thereby preventing a piezoelectric deterioration phenomenon in which an electric characteristic deteriorates. 
         [0045]    The pair of upper plates  122  are arranged in parallel to each other as large as for example, the width of the lower plate  121 , and as a result, the weight body  130  may be placed between the pair of upper plates  122 . The weight body  130  as a medium that maximally increases vibration force is inclined upward toward both ends from the center of the weight body  130  in order to prevent contact with the lower plate  121  of the vibration plate  120 . As described above, in a structure in which the vibration plate  120  includes the upper plate  122 , since the weight body  130  does not contact the lower plate  122 , the piezoelectric element  123  may be arranged on one flat surface of the lower plate  122 . 
         [0046]    For reference, the weight body  130  may be made of the metallic material and the weight body  130  is preferably made of a tungsten material having relatively high density in the same volume. 
         [0047]    The lower case  140  is formed by a generally elongated planar plate. In this case, the lower case  140  has a size and a shape to close the opened bottom surface of the upper case  110 . 
         [0048]    The upper case  110  and the lower case  140  may be coupled to each other in various methods such as caulking, welding, and bonding which have already widely been known to those skilled in the art. 
         [0049]      FIG. 3  is a front view schematically illustrating the piezoelectric vibration module according to the first preferred embodiment of the present invention except for an upper case. The vibration plate  120  is spaced apart from the lower case  140  in parallel with each other with a predetermined gap therebetween. Preferably, the lower plate  121  of the vibration plate  120  is coupled and fixed to both ends of the lower case  140  through steps formed at both ends thereof. Besides, the lower plate  121  is positioned on the lower case  140  with protrusions (not illustrated) at both ends thereof to form a space between the lower case  140  and the lower plate  121 . 
         [0050]    As illustrated above, the piezoelectric vibration module  100  according to the first preferred embodiment of the present invention includes the vibration plate  120 , in more detail, a stopper  125  at an edge of the lower plate  121 . Preferably, the stopper  125  is formed integrally with the lower plate  121 . In this case, the stopper  125  may be fixed by various coupling methods. 
         [0051]    The stopper  125  is made of the same material as the lower plate  121  and is preferably made of a rigid material which is not almost elastically transformed due to a high elastic coefficient thereof. The stopper  125  of the present invention is not limited thereto and may be made of a flexible material. 
         [0052]    In particular, the stopper  125  may prevent the piezoelectric element  123  from being damaged due to direct contact between the lower plate  121  or the piezoelectric element  123  and the lower case  140  when the piezoelectric vibration module  100  of the present invention is externally shocked, particularly, when the piezoelectric vibration module  100  drops or when the piezoelectric element  123  collides with the internal constituent members depending on the increase of the driving variation of the piezoelectric element  123 . To this end, the stopper  125  extends vertically downward at the edge of the lower plate  121  and extends shorter than a spaced distance between the lower plate  121  and the lower case  140  so as not to influence driving of the vibration plate  120 . That is, the stopper  125  is spaced apart from the lower case  140  with a predetermined gap therebetween without directly contacting the lower case  140 . 
         [0053]    The stopper  125  preferably extends more than the thickness of the piezoelectric element  123  attached to the lower plate  121 . The piezoelectric element  123  attached to the lower plate  121  does not contact the lower case  140  in unexpected driving variation of the lower plate  121 . 
         [0054]    The stopper  125  extends vertically downward at the edge of the lower plate  121  that extends in a longitudinal direction (long side) as described above. Therefore, preferably, the stopper  125  is formed vertically downward at edges close to both ends of the lower plate  121 , while the stopper is symmetrically placed at the center of the lower plate  121 . Alternatively, the stopper  125  may extend vertically downward at the edge of the lower plate  121  that extends in a crossing direction (short side). 
         [0055]    The stopper  125  may be formed at only one edge between two edges that extend in the longitudinal direction of the lower plate  121  or at two edges. In the latter case, the stoppers  125  that are arranged in parallel with each other are spaced apart from each other in the same as or more than the width of the piezoelectric element  123 . 
         [0056]    As a result, the vibration plate  120  may improve drop reliability by protecting the piezoelectric element  123  and the lower case  140  to protect the contact between the piezoelectric element  123  and the lower case  140  at the time of moving vertically. 
         [0057]    When power is applied to the piezoelectric element  123 , the piezoelectric element  123  is fully attached to the lower plate  121 , such that a movement occurs at the center of the lower plate  121  through extension or shrinkage deformation. Since the movement occurs while the lower plate  121  is fixed to both ends of the lower case  140 , the center of the vibration plate  120  is deformed vertically. 
         [0058]    Moreover, the piezoelectric element  123  may be configured to be stacked in a single-layer type or a multi-layer type. The piezoelectric element stacked in the multi-layer type may ensure an electric field required to drive the piezoelectric element at lower external voltage. Therefore, driving voltage of the piezoelectric vibration module  100  according to the present invention may be lowered, and as a result, in the present invention, the piezoelectric element  123  stacked in the multi-layer type is preferably adopted. 
         [0059]    As widely known to those skilled in the art, the piezoelectric element  123  may be made of various materials and particularly, made of polymer. 
         [0060]    The piezoelectric vibration module according to the present invention may further include a rubber damper (not illustrated) together with the stopper. Alternatively, in the piezoelectric vibration module of the present invention, the rubber damper made of the elastic material is placed between the vibration plate and the upper case and between the vibration plate and the lower case to serve to absorb shock among the respective constituent members while driving. 
         [0061]      FIGS. 4A to 4C  are diagrams illustrating a driving process of the piezoelectric vibration module  100  illustrated in  FIG. 3 . The piezoelectric vibration module  100  according to the first preferred embodiment of the present invention is coupled to an image display unit such as a touch screen panel or an LCD to transfer vibration force to the outside. 
         [0062]      FIG. 4A  is a front view of the piezoelectric vibration module  100  before external power is applied.  FIG. 4B  is a front view of the piezoelectric vibration module  100  in which the length of the piezoelectric element  123  is increased when power is applied. When the length of the piezoelectric element  123  increases, deformation rate of the lower plate  121  is relatively small and the lower plate  121  is fixed to the lower case  140 , and as a result, the vibration plate  120  is bent and driven downward. When the piezoelectric element  123  extends, the vibration plate  120  varies to be close to the lower case  140  while the driving variation of the vibration plate  120  is increased due to the drop or abnormal activation of the piezoelectric element  123 , thereby causing unnecessary collision. In this case, the stopper  125  of the vibration plate  120  contacts the lower case  140  to prevent the piezoelectric element  123  from being broken due to impact force. 
         [0063]      FIG. 4C  is a front view of the piezoelectric vibration module  100  in which the length of the piezoelectric element  123  is decreased when power is applied. When the length of the piezoelectric element  123  decreases, the lower plate  121  is bent and driven upward. 
         [0064]    As illustrated in the figure, a user of a haptic device with the piezoelectric element  123  may sense vibration feedback by vertical vibration. 
         [0065]    As illustrated in  FIG. 5 , a piezoelectric vibration module  100 ′ according to a second preferred embodiment of the present invention includes a stopper  125  at the center of the lower plate  121 . The stopper  125  is formed integrally with the lower plate  121 . In this case, the stopper  125  is not limited thereto, however, the stopper may be fixed by various coupling methods. 
         [0066]    The stopper  125  extends vertically downward at the center (in other words, a junction point between the lower plate  121  and the upper plate  122 ) of the vibration plate  120 , in particular, the lower plate  121  and the length of the stopper  125  should be shorter than the spacedc distance between the flat lower palate  121  and the lower case  140  which are arranged in parallel with each other. 
         [0067]    The stopper  125  preferably extends more than the thickness of the piezoelectric element  123  attached to the lower plate  121 . The piezoelectric element  123  attached to the lower plate  121  does not contact the lower case  140  in unexpected driving variation of the lower plate  121 . 
         [0068]    The stopper  125  may be made of the same material as the lower plate  122 . The stopper  125  is made of the rigid material, and as a result, since the stopper  125  has a high elastic coefficient, the stopper  125  is made of a rigid material which is not almost elastically transformed. The stopper  125  of the present invention may be made of the flexible material as necessary. 
         [0069]    According to preferred embodiments of the present invention, there is provided a piezoelectric vibration module that can prevent a driving body configured by a piezoelectric element capable of providing vibration force from directly colliding with internal constituent members. 
         [0070]    In particular, the piezoelectric vibration module includes a collision absorbing member that can protect the piezoelectric element without influencing the vibration force generated by activation of the piezoelectric element. 
         [0071]    Although the embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the present invention is not limited thereto, and 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. 
         [0072]    Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.