Abstract:
There is provided a piezoelectric vibration actuator including: a flat cover member; a vibration portion including a vibration plate that is spaced apart from the cover member in parallel by a predetermined distance and a piezoelectric element that generates a vibration force by repeatedly expanding and contracting according to power applied from the outside; a weight portion disposed on the vibration portion to increase the vibration force of the piezoelectric element; and a binding member fixing the vibration portion and the weight portion. 
     In addition, an enclosure portion is interposed between the weight portion and the vibration portion to enclose the center areas of the vibration portion, thereby making it possible to protect the piezoelectric element.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2014-0136888, filed on Oct. 10, 2014, entitled “Piezoelectric Vibration Actuator” which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND 
       [0002]    The present disclosure relates to a piezoelectric vibration actuator. 
         [0003]    In general, a vibration function is used for various uses in portable electronic devices such as a mobile phone, an E-book terminal, a game player, or a portable multimedia player (PMP). 
         [0004]    In particular, a vibration generating device for generating vibration is usually mounted in a portable electronic device and used as an alarm in the form of a soundless reception signal. 
         [0005]    According to multi-functionality of portable electronic devices, not only a compact size but also integration and various high-functionality are required from a vibration generating device. 
         [0006]    Recently, according to the demand of users to use a portable electronic device easily, a touch-type device in which information is input by touching the portable electronic device is generally selected, and a haptic module, which is a type of haptic interface, may also be applied so as to provide a user with an easier and more convenient communication with a computer or a program. “Haptic” which refers to tactile recognition contains not only the concept of inputting information by touching but also the concept of diversifying feedback to a touch by reflecting intuitive experience of a user, in an interface. 
         [0007]    Patent document 1 disclosing a method of generating a vibration force using a piezoelectric element discloses that a lower plate and an upper plate are formed as an integral single component, and thus convenience in regard to assembly may be provided. However, if an impact is applied to a vibration plate in a length direction thereof due to unexpected dropping collision, stress may be concentrated on a bonding portion between the lower plate and the upper plate, and a weight body may not be maintained and held via the vibration plate due to damages such as cracks. 
       RELATED ART DOCUMENT 
     Patent Document 
       [0008]    (Patent Document 1) Korean Patent Laid-Open Publication No. KR 10-2013-0125170 
       SUMMARY 
       [0009]    An aspect of the present disclosure may provide a piezoelectric vibration actuator in which a vibration portion including a piezoelectric element and a weight portion are assembled using a banding scheme so as to provide a degree of freedom to the vibration portion and the weight portion. 
         [0010]    According to an aspect of the present disclosure, a piezoelectric vibration actuator may be provided, in which, by using a binding member formed of a banding member such as a tape or a ring-shaped band, a reliable binding state between a weight portion and a vibration portion may be secured even against not only vertical flexural vibration due to a vibration force but also traverse impact due to abnormal collision. 
         [0011]    According to another aspect of the present disclosure, a piezoelectric vibration actuator may include: a flat cover member; a vibration portion including a vibration plate that is spaced apart from the cover member in parallel by a predetermined distance and a piezoelectric element that generates a vibration force by repeatedly expanding and contracting according to power applied from the outside; a weight portion disposed on the vibration portion to increase the vibration force of the piezoelectric element; and a binding member fixing the vibration portion and the weight portion. 
         [0012]    According to another aspect of the present disclosure, an enclosure portion may be interposed between the weight portion and the vibration portion, and the weight portion, the vibration portion, and the enclosure portion are bound to each other using binding member formed of a banding member such as a tape or a ring-shaped band, thereby closely adhering and fixing them to each other. 
         [0013]    According to another aspect of the present disclosure, the piezoelectric element disposed in a center area of the vibration portion may be protected by using the enclosure portion enclosing the center area of the vibration portion in the piezoelectric vibration actuator. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]    The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0015]      FIG. 1  is a perspective view of a piezoelectric vibration actuator according to an exemplary embodiment of the present disclosure; 
           [0016]      FIG. 2  is a cross-sectional view of a piezoelectric vibration actuator according to an exemplary embodiment of the present disclosure, cut along a line II-II of  FIG. 1 ; 
           [0017]      FIG. 3  is a schematic disassembled perspective view of a piezoelectric vibration actuator according to an exemplary embodiment of the present disclosure; 
           [0018]      FIG. 4  is a perspective view of a piezoelectric vibration actuator according to another exemplary embodiment of the present disclosure; 
           [0019]      FIG. 5  is a cross-sectional view illustrating a piezoelectric vibration actuator according to another exemplary embodiment of the present disclosure, cut along a line V-V of  FIG. 4 ; 
           [0020]      FIG. 6  is a schematic disassembled perspective view of a piezoelectric vibration actuator according to another exemplary embodiment of the present disclosure; and 
           [0021]      FIG. 7  is a cross-sectional view illustrating a piezoelectric vibration actuator according to another exemplary embodiment of the present disclosure, cut along a line VII-VII of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The objects, features and advantages of the present disclosure will be more clearly understood from the following detailed description of the exemplary 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 disclosure, when it is determined that the detailed description of the related art would obscure the gist of the present disclosure, the description thereof will be omitted. 
         [0023]    Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
         [0024]    The present disclosure relates to a piezoelectric vibration actuator  1  which is capable of transmitting a vibration force of a piezoelectric element to external components via repeated contraction and expansion. 
         [0025]    Referring to  FIGS. 1 through 3 , the piezoelectric vibration actuator  1  according to an exemplary embodiment of the present disclosure is a device that generates a vibration force in, for example, a touch screen panel (not shown), and is surrounded by a case  100  and a cover member  900 , and includes a vibration portion  400  that is linearly driven by flexurally vibrating in a vertical direction according to power applied to a flexible printed circuit board  500  or a printed circuit board. Also, the piezoelectric vibration actuator  1  according to an exemplary embodiment of the present disclosure includes a weight portion  200  in its inner space. 
         [0026]    The case  100  may have a slim and long, rectangular box shape with one opened surface (for example, a lower surface), and may accommodate the vibration portion  400 , that is, a piezoelectric element  410  and a vibration plate  420 . As illustrated in  FIGS. 1 through 3 , the one opened surface of the case  100  of the piezoelectric vibration actuator  1  according to an exemplary embodiment of the present disclosure may be covered with the cover member  900  so as to close the inner space of the case  100 . Here, the case  100  may also have other shapes than the illustrated rectangular box shape according to the shape and size of a vibration portion. Also, the cover member  900  has the size and shape that may close the one opened surface of the case  100 . 
         [0027]    The case  100  and the cover member  900  may be coupled to each other using various methods that are well-known to one of ordinary skill in the art, such as caulking, welding or bonding. 
         [0028]    The piezoelectric vibration actuator  1  according to the present disclosure is driven using the vibration portion  400  that generates a vibration force in a vertical direction via translational motion of the piezoelectric element  410  that repeats expansion and contraction according power applied from the outside as described above. 
         [0029]    As illustrated in  FIGS. 2 and 3 , the vibration portion  400  is formed of the piezoelectric element  410  and the vibration plate  420 . The vibration portion  400  is electrically connected to the flexible printed circuit board  500  that applies power to drive the piezoelectric element  410 . Here, for clear understanding of the present disclosure, description of wiring between the piezoelectric element  410  and the flexible printed circuit board  500  will be omitted. 
         [0030]    When power is applied to the piezoelectric element  410  via the flexible printed circuit board  500 , as the piezoelectric element  410  is completely attached to the vibration plate  420 , moment is generated with respect to a center portion of the vibration plate  420  via expansion and/or contraction. As moment is generated in the vibration plate  420  while the vibration plate  420  is fixed to an inner surface of the case  100  of the piezoelectric vibration actuator  1  facing the vibration plate  420 , the center portion of the vibration plate  420  is flexurally deformed in the vertical direction. In order to prevent direct collision between the piezoelectric element  410  and the cover member  900  due to displacement of the vibration plate  420  in the vertical direction, the vibration plate  420  may preferably be spaced apart upwardly from the cover member  900  by a predetermined distance (in consideration of displacement of the vibration plate  420 ). As is well-known to one of ordinary skill in the art, the piezoelectric element  410  may be formed of various materials such as polymer or ceramic. 
         [0031]    As described above, the vibration plate  420  is repeatedly expanded or contracted as a single body with the piezoelectric element  410  disposed on the lower surface of the vibration plate  420  so as to transmit a vibration force of the piezoelectric element  410  to external components. The vibration plate  420  is generally in the form of a flat plate. The piezoelectric element  410  is mounted on one flat surface of the vibration plate  420 , specifically, on the lower surface thereof, and the weight portion  200  is disposed on the other surface of the vibration plate  420 , specifically, on an upper surface thereof. 
         [0032]    The vibration plate  420  may be formed of a metal material having elasticity, such as steel use stainless (SUS), so that the vibration plate  420  may be deformed integrally with the piezoelectric element  410  which repeats expansion and contraction according to power applied from the outside via the flexible printed circuit board  500 . Also, if the vibration plate  420  and the piezoelectric element  410  are bonded to each other using a bonding method, the vibration plate  420  may be formed of Invar which is a material having a similar coefficient of thermal expansion as that of the piezoelectric element  410  in order to prevent bending that may be caused due to hardening of an adhesive material. As described above, the vibration plate  420  is formed of an Invar material having a similar coefficient of thermal expansion as that of the piezoelectric element  410 , and thus, thermal stress in the piezoelectric element  410  which is generated due to an operation or thermal impact under a high-temperature external environment may be reduced, thereby preventing piezoelectric deterioration whereby electrical characteristics are degraded. 
         [0033]    In addition, the vibration plate  420  may also be formed of a pair of first plates spaced apart from each other and a second plate that connects the pair of first plates, as illustrated in  FIG. 6 . 
         [0034]    As illustrated in  FIGS. 2 and 3 , the vibration plate  420  of the vibration portion  400  is spaced apart from the cover member  900  in parallel by a predetermined distance, and preferably, mounting portions  910  are formed at two ends portions of the cover member  900 . The mounting portions  910  may provide space between the vibration plate  420  and the cover member  900 . 
         [0035]    The case  100  includes blocks  110  each disposed on inner surfaces thereof facing each other, for example, on inner surfaces of a left side wall and a right side wall, so as to correspond to the mounting portions  910 . As illustrated in  FIG. 2 , the blocks  110  protrude from the inner surfaces of the case  100  toward a center portion at the same height as the weight portion  200  which is to be disposed in the inner space formed by the case  100  and the cover member  900 . In addition, the blocks  110  downwardly press two end portions of the vibration plate  420  arranged on the mounting portions  910 . Accordingly, the vibration plate  420  may be firmly fixed, thereby maximizing moment and enabling reliable flexural vibration. 
         [0036]    Here, the two blocks  110  may preferably be spaced apart from each other by a greater distance than a length portion of the weight portion  200  so that reciprocal motion of the weight portion  200  in a vertical direction is not disturbed. The blocks  110  may prevent damage to the piezoelectric element  410  by using contact between the two end portions of the weight portion  200  and the inner surface of the case  100  if an external impact is applied to the piezoelectric vibration actuator  1  according to the present disclosure, particularly, if a lengthwise impact (traverse direction) is applied to the piezoelectric vibration actuator  1 . If a traverse impact is applied, the weight portion  200  may reduce an amount of lengthwise movement of the piezoelectric vibration actuator  1  by using the blocks  110 , thereby protecting the piezoelectric element  410  and also improving drop reliability at the same time. 
         [0037]    Selectively, the blocks  110  may be formed of the same material as the case  100 , and of a rigid material which has a high modulus of elasticity and is thus hardly elastically deformed. The blocks  110  are not limited thereto, and may also be formed of a soft material such as a damper in order to mitigate impact. 
         [0038]    The vibration portion  400  includes the weight portion  200  on the vibration plate  420  as described above, and the weight portion  200  is fixed to the vibration plate  420  by using a binding member  600 . The binding member  600  binds the weight portion  200  and the center portion of the vibration plate  420  with each other so that they are adhered to each other. According to necessity, a two-sided tape may be interposed between the vibration plate  420  and the weight portion  200  to facilitate fixation thereof. 
         [0039]    Here, the weight portion  200  may have a bar shape as illustrated in  FIG. 3  and as a medium that maximizes a vibration force of the vibration portion  400 . Also, the weight portion  200  is upwardly inclined from the center portion of the weight portion  200  to the two end portions thereof in order to prevent contact with the vibration plate  420  when the weight portion  200  is flexurally vibrated. In addition, in the piezoelectric vibration actuator  1  according to the present disclosure, the case  100  is spaced apart from an upper portion of the weight portion  200  by a predetermined distance so that the weight portion  200  does not contact or collide with the upper inner surface of the case  100  unnecessarily even when the vibration plate  420  of the vibration portion  400  is being driven to be displaced and bent upwardly. 
         [0040]    For reference, the weight portion  200  may be formed of a metal material, and preferably, of a tungsten which has a relatively high density per a unit volume. 
         [0041]    Selectively, a concave portion  210  is formed in an outer circumferential surface of a center area of the weight portion  200 . The concave portion  210  may have a form that receives the binding member  600  so that a coupling position of the binding member  600  may be confirmed, and moreover, traverse movement of the binding member  600  may be restricted using the concave portion  210 . 
         [0042]    The binding member  600  couples the center area of the weight portion  200  and a center area of the vibration portion  400  as illustrated in  FIGS. 2 and 3 , and a banding member such as a tape is used as the binding member  600 . Selectively, the binding member  600  may be formed of an elastic soft material to continuously tighten the weight portion  200  and the vibration portion  400  so that clearance does not occur even during flexural vibration. Thus, the binding member  600  may be formed of a contractible soft material. 
         [0043]    In addition, the binding member  600  may be in the form of a ring-shaped band as illustrated in  FIG. 3 . 
         [0044]    The binding member  600  does not fix the weight portion  200  and the vibration plate  420  of the vibration portion  400  using a conventional fixing method such as a fixing method using a bracket or a fixing method by using a bonding method, and thus minimizes a stress in a bonding portion between the weight portion  200  and the vibration portion  400  in a case of dropping collision or traverse impact and secures reliable binding of the weight portion  200  and the vibration portion  400 . In addition, the binding member  600  is mounted by enclosing the weight portion  200  and the vibration portion  400  in the form of a ring-shaped band or a tape, and thus convenience in terms of assembly is additionally provided. 
         [0045]    In other words, the piezoelectric vibration actuator  1  according to an exemplary embodiment of the present disclosure has a structure, in which fixation of the weight portion  200  and the vibration portion  400  is facilitated via a tension operation of the binding member  600 , and also, as the two components are not fixed as a single body, if external impact is applied, flexibility is provided to the bonding portion and an external force applied to one component is not transmitted to the other component. 
         [0046]    In addition, the piezoelectric element  410  may be a single-layered structure or stacked in a multi-layered structure. Piezoelectric elements stacked in a multi-layered structure may secure an electrical field required to drive the piezoelectric elements even at a low external voltage. This may provide the effect of reducing a driving voltage of the piezoelectric vibration actuator according to the present disclosure, and thus, the piezoelectric elements stacked in a multi-layered structure may be preferably used in the present disclosure. 
         [0047]    In the piezoelectric vibration actuator  1  according to an exemplary embodiment of the present disclosure, an impact buffer member  700  capable of protecting the weight portion  200  or the vibration portion  400  without affecting a vibration force generated by activation of the piezoelectric element  410  is formed on an upper inner surface of the case  100  and an upper surface of the cover member  900 . Selectively, the impact buffer member  700  may be formed of a poron material reducing vibration and noise when the vibration portion  400 , the weight portion  200 , the case  100 , or the cover member  900  contact one another. 
         [0048]      FIGS. 4 through 7  are schematic views illustrating a piezoelectric vibration actuator  1 ′ according to another exemplary embodiments of the present disclosure. 
         [0049]    In detail, the piezoelectric vibration actuator  1 ′ according to another exemplary embodiment of the present disclosure has a very similar structure to that of the piezoelectric vibration actuator  1  illustrated in  FIGS. 1 through 3  except for an arrangement of the weight portion  200  and the vibration portion  400 , and thus, for clear understanding of the present closure, description of similar or identical components will be omitted. 
         [0050]    The piezoelectric vibration actuator  1 ′ according to another exemplary embodiment of the present disclosure is formed of the case  100  having one opened surface, the cover member  900  that closes the one opened surface, the vibration portion  400  that linearly drives due to expansion and/or contraction of the piezoelectric element  410  in inner space defined by the case  100  and the cover member  900 , the weight portion  200  disposed on the vibration portion  400 , the binding member  600  that binds the vibration portion  400  and the weight portion  200  at circumferences of the vibration portion  400  and the weight portion  200 , and an enclosure portion  300  interposed between the vibration portion  400  and the weight portion  200 . 
         [0051]    In particular, in the piezoelectric vibration actuator  1 ′ according to another exemplary embodiment of the present disclosure, the enclosure portion  300  is disposed between the weight portion  200  and the vibration portion  400  as illustrated in  FIGS. 5 through 7  to enclose the center area of the vibration portion  400 . 
         [0052]    The enclosure portion  300  is a component having a reverse U-shaped cross-section as illustrated in  FIGS. 6 and 7 , and includes a leg portion  320  that extends vertically downward from two edges of a flat surface  310 . The leg portion  320  of the enclosure portion  300  extends by a greater size than a sum of thicknesses of the piezoelectric element  410  and the vibration plate  420 . When the vibration portion  400  flexurally vibrates in a vertical direction, the leg portion  320  performs the function as a stopper that restricts downward displacement of the vibration plate  420 , and thus may prevent direct collision between the piezoelectric element  410  disposed under the vibration plate  420  and the cover member  900 . 
         [0053]    The flat surface  310  of the enclosure portion  300  allows the lower surface of the weight portion  200  and an upper surface of the vibration plate  420  of the vibration portion  400  to face each other, and the vibration plate  420  is not disposed directly under the weight portion  200 . Accordingly, the vibration plate  420  is protected from abnormal driving of the weight portion  200 . Preferably, the flat surface  310  of the enclosure portion  300  extends to be longer than a length of the piezoelectric element  410  so as to cover the piezoelectric element  410  overall. 
         [0054]    Selectively, the enclosure portion  300  facilitates coupling of respective components by using a two-sided tape  330  between a lower surface of the flat surface  310  and the upper surface of the vibration plate  420 . 
         [0055]    The piezoelectric vibration actuator  1 ′ according to another exemplary embodiment of the present disclosure binds center portions of the weight portion  200  and the enclosure portion  300  and the vibration portion  400  by using the binding member  600  so that they are adhered to one another. As illustrated in  FIG. 5 , the binding member  600  is coupled to the center area of the weight portion  200  and the center area of the piezoelectric element  410  of the vibration portion  400  at circumferences thereof by using a banding member such as a tape or a ring-shaped band. In order that the binding member  600  encloses the lower surface of the piezoelectric element  410 , the leg portion  320  of the enclosure portion  300  is formed at two edges of the flat surface  310  at two end portions except a center portion of the flat surface  310 . Accordingly, the binding member  600  is disposed in the center area of the weight portion  200  and is wound between the leg portions  320  disposed symmetrically as illustrated in  FIG. 6 . Consequently, binding of the center area of the weight portion  200  and the center area of the vibration portion  400  is facilitated using the binding member  600 . 
         [0056]    The vibration plate  420  illustrated in  FIG. 3  which is thin and long may be replaced by a vibration plate  420  formed of three components according to the present disclosure. Referring to  FIG. 6 , the vibration plate  420  may be formed of a pair of first plates  421  and a second plate  422 , and the pair of first plates  421  may be spaced apart from each other, preferably, by a distance that is greater than a length of the piezoelectric element  410 . Alternatively, a length of the second plate  422  may be greater than the length of the piezoelectric element  410 . The piezoelectric element  410  is disposed on a lower surface of the second plate  422 . The second plate  422  is disposed between the first plates  421  spaced apart from each other, and is connected to the pair of first plates  421  in various manners. Preferably, the pair of first plates  421  may be coupled to the lower surface of the second plate  422  at two ends of the second plate  422 , and the piezoelectric element  410  is disposed in space defined by the lower surface of the second plate  422  and the pair of first plates  421 . 
         [0057]    Preferably, the pair of first plates  421  may be formed of a metal material that is subject to deformation of a piezoelectric element and elastic, such as a SUS. Also, the second plate  422  may be formed of an Invar material having a similar coefficient of thermal expansion as that of the piezoelectric element  410 . However, the first and second plates  421  and  422  are not limited thereto, and may be formed of other various materials. 
         [0058]    Although the embodiments of the present disclosure have been disclosed for illustrative purposes, it will be appreciated that the present disclosure 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 disclosure. 
         [0059]    Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the disclosure, and the detailed scope of the disclosure will be disclosed by the accompanying claims.