JP5036013B1 - Piezoelectric device - Google Patents

Abstract

A piezoelectric device including a plate-like piezoelectric element, a metal plate, and a support member. The metal plate can be thinned in a piezoelectric device supported by the support member, and a piezoelectric device suitable as an acceleration sensor is provided. To do.
A plate-like piezoelectric element, a metal plate, and a support member are provided. The piezoelectric element and the support member are fixed to only one surface of the metal plate, and the metal plate is supported by the support member. Thus, the thickness is obtained by adding the thickness of the metal plate 2 and the thickness of the piezoelectric element 1 or the support member 3.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric device using a piezoelectric effect, and more particularly to a piezoelectric device suitably used as an acceleration sensor.

  FIG. 9 is a perspective view of a piezoelectric device in Patent Document 1 as a prior art. FIG. 9 shows a piezoelectric acceleration sensor including a piezoelectric element 1 polarized in a predetermined direction, a metal plate 2, and a support member 3.

  The support member 3 includes a substrate circuit portion and a substantially planar substrate base portion protruding from the end portion of the substrate circuit portion. Further, one plate surface of the metal plate 2 is supported and fixed to one surface of the substrate base portion, and the other plate surface of the metal plate is piezoelectric so that the piezoelectric element 1 and the substrate base portion do not overlap in a predetermined direction. Element 1 is supported and fixed.

International Publication No. 2011/043219

  The thickness of the piezoelectric device described in Patent Document 1 is the sum of the thicknesses of the piezoelectric element, the metal plate, and the support member. In order to reduce the thickness of the piezoelectric device, all of the piezoelectric element, the metal plate, and the supporting member must be reduced, and there is a problem that there is a limit to such reduction in thickness.

  The present invention solves the above-described problem by providing a piezoelectric device including a plate-like piezoelectric element, a metal plate, and a support member, and the piezoelectric element and the support member are fixed only on one side of the metal plate, and the metal plate is supported by the support member. To solve.

  That is, since the piezoelectric element and the support member are fixed only on one side of the metal plate, the thickness of the piezoelectric device is the sum of the metal plate and the support member when the piezoelectric element is thinner than the support member. When the support member is thinner than the piezoelectric element, the thickness is the sum of the thickness of the metal plate and the piezoelectric element.

  In addition, a case that accommodates at least a part of the piezoelectric element, the metal plate, and the support member is provided, and by fixing the support member to the case, the maximum of the metal plate is between the metal plate and the case and between the piezoelectric element and the case A piezoelectric device provided with a gap larger than the vibration amplitude may be used.

  By fixing the support member with the case, it is possible to reduce the thickness while ensuring a gap in which the piezoelectric element can vibrate. Furthermore, since the piezoelectric element, the metal plate, and the support member are accommodated in the case, when the piezoelectric device is attached, an arbitrary place on the case can be held, so that attachment workability is improved.

  Further, the thickness dimension of the support member is preferably larger than the dimension obtained by combining the thickness dimension of the piezoelectric element and the maximum vibration amplitude.

  By adopting such a configuration, it is possible to ensure a gap that allows the piezoelectric element to vibrate without providing an extra recess in the case.

  In addition, an external electrode is formed on the surface of the piezoelectric element that is not fixed to the metal plate, a connection electrode is formed on the surface of the support member that is not fixed to the metal plate, and the external electrode and the connection electrode are conductively connected by the connection conductor. The support member supports at least one of the long-side end portions of the metal plate, and the external electrode and the connection conductor are conductively connected in the vicinity of the end portion in the long-side direction of the piezoelectric element. A piezoelectric device that is routed along the direction may be used.

  The connection conductor is fixed near the center of the end in the long side direction of the piezoelectric element, and the connection conductor is routed along the long side direction. Therefore, the piezoelectric element is twisted with respect to the long side direction due to the influence of the connection conductor. Abnormal vibration that vibrates can be prevented.

  Alternatively, the case may be a piezoelectric device in which the case is made conductive and the external electrode and the case are electrically connected by an elastic conductor.

  According to the present invention, a thin piezoelectric device can be provided.

The figure which showed an example of the piezoelectric device in this invention. 1A is a perspective view, and FIG. 1B is a cross-sectional view taken along the AA plane in FIG. The figure which showed an example of the piezoelectric device in this invention. 2A is a perspective view, and FIG. 2B is a plan view of the case 5 in FIG. The figure which showed an example of the piezoelectric device in this invention. 3 (a) and 3 (b) are cross-sectional views along the BB plane of FIG. 2 (a). The figure which showed an example of the piezoelectric device in this invention. 4A is a perspective view, and FIG. 4B is a cross-sectional view taken along the AA plane in FIG. The figure which showed an example of the piezoelectric device in this invention. FIG. 5A is a perspective view, and FIG. 5B is a cross-sectional view taken along the AA plane in FIG. The figure which showed an example of the piezoelectric device in this invention. FIG. 6A is a perspective view, and FIG. 6B is a cross-sectional view taken along the AA plane in FIG. The figure which showed an example of the piezoelectric device in this invention. 7A is a perspective view, and FIG. 7B is a cross-sectional view taken along the AA plane in FIG. 7A. The figure which showed an example of the piezoelectric device in this invention. FIG. 8A is a perspective view, and FIG. 8B is a cross-sectional view taken along the AA plane in FIG. The perspective view of the piezoelectric device in patent document 1. FIG.

  Embodiments of the present invention will be described with reference to the drawings.

  Fig.1 (a) is a perspective view which shows an example of the piezoelectric device in this invention. Moreover, FIG.1 (b) is sectional drawing in the AA surface of Fig.1 (a).

  In FIG. 1, an external electrode 11 is formed on the surface of a plate-like piezoelectric element 1 by sputtering or the like, and the back surface of the piezoelectric element 1 is fixed to the center of a metal plate 2 with an adhesive or the like.

  Both ends in the longitudinal direction of the metal plate 2 are fixed on the back surface of the support member 3 such as a circuit board with solder or a conductive adhesive.

  Thus, since the piezoelectric element 1 is arranged in the empty space at the center of the metal plate 2 supported at both ends by the support member 3, the piezoelectric device can be made thin.

  A connection electrode 31 is provided on the surface of the support member 3, and the connection electrode 31 and the external electrode 11 are electrically connected by a connection conductor 4.

  In addition, as a connection conductor 4, a lead wire, a plate-shaped terminal, a spring terminal, a flexible substrate, etc. can be used, However, it is not restricted to these. In addition, by using a plate-shaped conductor that is wide enough not to disturb the vibration of the piezoelectric element 1, the possibility of peeling or disconnection of the conductive connection portion can be further reduced, and the reliability of the conductive connection can be reduced. improves. Further, if the connecting conductor is a plate-like conductor that is wide enough not to disturb the vibration of the piezoelectric element 1, assembly by an automatic assembly machine is possible, so that assembly accuracy can be improved and processing man-hours can be reduced.

  The connection conductor 4, the connection electrode 31, and the external electrode 11 can be electrically connected by solder, a conductive adhesive in which a conductive filler is dispersed in an adhesive, or the like, but is not limited thereto.

  In addition, since the piezoelectric element 1 is a rectangular plate, the metal plate 2 is supported by the support member 3 having a dimension equal to or longer than the length of the long side direction of the metal plate 2 near both ends in the long side direction of the piezoelectric element 1. The piezoelectric element 1 vibrates at the center in the long side direction. Further, it is desirable to provide a sufficient gap between the piezoelectric element 1 and the support member 3 so as not to hinder the vibration of the piezoelectric element 1, and between the long side surface of the piezoelectric element 1 and the side surface of the support member 3. In order to provide a gap, it is desirable that the fixing portion of the metal plate 2 on the support member 3 is disposed so as to leave a margin from the roots and the tips on the arm portions 311 and 312. Further, it is desirable to provide a gap between the side surface of the short side of the piezoelectric element 1 and the side surfaces of the arm portions 311, 312. If the gap dimension between the arm portions 311, 312 is equal, the piezoelectric element The position of the vibration antinode of 1 and the position of the vibration antinode of the metal plate 2 are more preferable.

  Note that the connection portion between the external electrode 11 and the connection conductor 4 may be at the end in the long side direction of the piezoelectric element 1 because vibration may be suppressed by the connection conductor 4.

  Further, if there is a connection portion between the external electrode 11 and the connection conductor 4 at the end portion in the short side direction perpendicular to the long side direction in the surface of the piezoelectric element 1, the piezoelectric element 1 induces vibration that twists in the long side direction. Therefore, it is desirable that the piezoelectric element 1 is in the center of the short side direction.

  A cable 301 is connected to the support member 3 and plays a role such as supply of drive power and extraction of the output of the piezoelectric device.

  As an example of a method of using a piezoelectric device, a case where the device is used as an acceleration sensor will be described. When acceleration acts on the piezoelectric device, the piezoelectric element 1 and the metal plate 2 bend, and a potential difference is generated between the front and back surfaces of the piezoelectric element 1.

  The potential on the surface of the piezoelectric element 1 is transmitted to the connection conductor 4, the connection electrode 31, and the support member 3 through the external electrode 11. On the other hand, the potential on the back surface of the piezoelectric element 1 is transmitted to the support member 3 through the metal plate 2.

  Furthermore, if a conductive path is provided in the support member 3, the potential difference between the front and back surfaces of the piezoelectric element can be taken out via the cable 301.

  If the support member 3 is provided with a detection circuit, an amplification circuit, and the like, and the potential difference between the front and back surfaces of the piezoelectric element 1 is detected and amplified with high accuracy, the acceleration can be detected with high sensitivity.

  Fig.2 (a) is a perspective view which shows an example of the piezoelectric device in this invention. FIG. 2B is a plan view of the case 5 in FIG.

  By sealing the piezoelectric device of FIG. 1 with the case 5 and the case lid 51, it is possible to prevent damage due to external impacts, etc., and corrosion and deterioration due to outside air. Further, if the case 5 and the case lid 51 are made of a conductor such as metal, the influence of electromagnetic noise from the outside can be prevented.

  For example, the case 5 is provided with recesses 501, 502, and 503, the recess 501 is slightly deeper than the height of the cable 301, the recess 502 is slightly deeper than the height excluding the metal plate of the piezoelectric device in FIG. 1, and the recess 503 is in FIG. The cable 301 is led out from the recess 501 by fixing the height including the metal plate of the piezoelectric device and the maximum vibration amplitude of the metal plate, the support member 3 is fixed to the recess 502, and the recess 501. 502 and 503 can accommodate the piezoelectric device of FIG.

  Furthermore, by fixing the case lid 51 to the case 5 with an adhesive or the like, the piezoelectric device of FIG. 1 can be sealed.

  In addition, when the connection conductor 4 and the connection electrode 31 approach the case cover part 51, the case cover part 51 is comprised with an insulator, or the connection conductor 4 and the connection electrode 31 vicinity on the case cover part 51 are made with an insulator. By covering, it is possible to prevent problems such as an electrical short circuit.

  FIG. 3A and FIG. 3B are cross-sectional views along the BB plane of FIG.

  In the configuration of FIG. 3A, a gap larger than the maximum vibration amplitude of the metal plate 2 is provided between the metal plate 2 and the inner wall bottom surface of the case 5. A gap larger than the maximum vibration amplitude of the piezoelectric element 1 is provided between the external electrode 11 of the piezoelectric element 1 and the case lid 51.

  It is desirable that the piezoelectric element 1 is thinner than the support member 3 so that the piezoelectric element 1 does not collide with the case lid 51 due to vibration.

  In FIG. 3B, which is a modification of FIG. 3A, the external electrode 11 of the piezoelectric element 1 faces the inner wall bottom surface of the case 5, and the external electrode 11 and the case 5 are conductively connected by the elastic conductor 41. .

  The case 5 is entirely made of a conductor such as metal, or a conductive path is formed from the conductive connection portion of the elastic conductor 41 to the support member 3.

  If the conductive path from the case 5 can be formed, the conductive path on the support member 3 can be a single side.

  Examples of the elastic conductor include conductive rubber, metal springs such as leaf springs and coil springs, but are not limited thereto.

  Further, in the configuration of FIG. 3B, since it is not necessary to provide a gap between the support member 3 and the bottom surface of the inner wall of the case 5, it can be made thinner than the configuration of FIG.

  Furthermore, if the space between the support member 3 and the bottom surface of the inner wall of the case 5 is directly fixed, the recess 502 of the case 5 can be omitted, so that the configuration of the case 5 can be further simplified.

  In addition, it is desirable to provide a gap between the metal plate 2 and the case lid 51 so that the metal plate 2 does not collide with the case lid 51 due to vibration.

  Similarly, it is desirable to make the piezoelectric element 1 thinner than the support member 3 so that the external electrode 11 of the piezoelectric element 1 does not collide with the inner wall bottom surface of the case 5 due to vibration.

  FIG. 4A is a perspective view showing another example of the piezoelectric device according to the present invention. FIG. 4B is a cross-sectional view taken along the AA plane in FIG.

  The point which is supported by the supporting member 3 only at one edge part of the metal plate 2 differs from FIG.

  The other end of the metal plate 2 that is not supported by the support member 3 may not extend from the piezoelectric element 1.

  The configuration of FIG. 4 is suitable when the number of circuit components is smaller than that of FIG.

  FIG. 5A is a perspective view showing another example of the piezoelectric device according to the present invention. FIG. 5B is a cross-sectional view taken along the AA plane in FIG.

  The point from which the support member 3 becomes only the part which supports one edge part of the metal plate 2 differs from FIG.

  The other end of the metal plate 2 that is not supported by the support member 3 may not extend from the piezoelectric element 1.

  The configuration of FIG. 5 is suitable when the number of circuit components is smaller than that of FIG.

  Fig.6 (a) is a perspective view which shows another example of the piezoelectric device in this invention. FIG. 6B is a cross-sectional view taken along the AA plane in FIG.

  FIG. 4 is different from FIG. 4 in that the support member 3 extends from one end of the metal plate 2.

  The other end of the metal plate 2 that is not supported by the support member 3 may not extend from the piezoelectric element 1.

  The configuration of FIG. 6 is suitable for a case where the number of circuit components is smaller than that of FIG.

  Fig.7 (a) is a perspective view which shows another example of the piezoelectric device in this invention. Moreover, FIG.7 (b) is sectional drawing in the AA surface of Fig.7 (a).

  The point which has arrange | positioned the piezoelectric element 1 in the through-hole part of the support member 3 center differs from FIG.

  The configuration of FIG. 7 is suitable when there are more circuit parts than in FIG. 1, when high functionality is required, and when the strength of the support member is required.

  FIG. 8A is a perspective view showing another example of the piezoelectric device according to the present invention. FIG. 8B is a cross-sectional view taken along the AA plane in FIG.

  1 is different from FIG. 1 in that the outer shape of the support member 3 is circular.

  The configuration of FIG. 8 is also suitable when there are more circuit parts than in FIG. 1, when higher functionality is required, and when the strength of the support member is required.

  An example of an embodiment of the present invention will be described.

  FIG. 1 shows an example of an embodiment of the present invention.

  The material of the piezoelectric element 1 was PbZrTiO3 ceramic, and electrodes were formed on the front and back surfaces. The dimensions are 4.0 mm in length, 1.6 mm in width, and 0.4 mm in thickness.

  The material of the metal plate 2 is phosphor bronze, and the dimensions are a length of 5.7 mm, a width of 1.6 mm, and a thickness of 0.1 mm.

  The piezoelectric element 1 was bonded to the center of the metal plate 2 with a thermosetting epoxy resin.

  The support member 3 has the shape shown in FIG. 1 and is made of a glass epoxy substrate having a thickness of 0.4 mm and an outer shape of which a rectangle of 1.7 mm × 0.5 mm protrudes from both ends of a square of 7 mm × 7 mm. .

  A conductive pattern for electrically connecting the piezoelectric element 1 and the cable 301 was formed on the square portion of the support member 3, and the cable 301 for outputting a signal was connected.

  The metal plate 2 and the support member 3 were fixed by conducting conductive connection with solder.

  The external electrode 11 and the connection electrode 31 were electrically connected by soldering using a conductive wire as a connection conductor.

  Further, the square portion of the support member 3 is bonded to the recess 502 of the case 5 made of SUS304 with a thermosetting epoxy resin, and the case lid portion 51 is fixed to the case 5 by press-fitting. Was made.

  The piezoelectric device of the present invention is also used as an acceleration sensor for detecting an impact generated on an electronic device and a vibration generated by the electronic device itself.

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 11 External electrode 2 Metal plate 3 Support member 31 Connection electrode 301 Cable 311 and 312 Arm part 4 Connection conductor 41 Elastic conductor 5 Case 51 Case cover part 501, 502, 503 Dimple

Claims (4)

A plate-like piezoelectric element; a metal plate; and a support member, wherein the piezoelectric element and the support member are fixed only to one side of the metal plate, and the metal plate is supported by the support member , An external electrode is formed on a surface not fixed to the metal plate, a connection electrode is formed on a surface not fixed to the metal plate of the support member, and the external electrode and the connection electrode are conductively connected by a connection conductor. The shape of the metal plate is a rectangular plate, and the support member supports at least one of the end portions in the long side direction of the metal plate, and the external portion is located near the center of the end portion in the long side direction of the piezoelectric element. the piezoelectric device of the connection conductor and the electrode and the conductive connection, the connection conductor, characterized in Rukoto routed along the long side direction. A plate-like piezoelectric element; a metal plate; a support member; a case accommodating the piezoelectric element and the metal plate; wherein the piezoelectric element and the support member are fixed only on one side of the metal plate; A plate is supported by the support member, an external electrode is formed on a surface of the piezoelectric element that is not fixed to the metal plate, the case has conductivity, and the external electrode and the case are connected by an elastic conductor. the piezoelectric device according to claim Tei Rukoto.   A case accommodating at least a part of the piezoelectric element, the metal plate, and the support member; the support member being fixed by the case; and between the metal plate and the case; and the piezoelectric element and the The piezoelectric device according to claim 1, wherein a gap that is larger than a maximum vibration amplitude of the metal plate is provided between the case and the case. The thickness of the support member, the piezoelectric device according to any one of claims 1 to 3, characterized in that greater than dimension combined the maximum vibration amplitude and the thickness of the piezoelectric element.

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