JP2005286125A - Piezoelectric element and piezoelectric actuator device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric element for actuator which is fixed to a fixing member near one end side of the lower face of a piezoelectric material, is fixed to a member to be moved at the near part of the other end of the lower face, is used to drive the member to be moved and in which the peeling of a fixing part of the fixing member and the member to be moved due to adhesive is hard to occur. <P>SOLUTION: In the piezoelectric material 12, first and second inner electrodes 13 and 14 are laminated and an active part where the first and second inner electrodes 13 and 14 are laminated is displaced by an application of AC voltage. The piezoelectric material 12 expands and contracts in a lengthwise direction. In the piezoelectric material 12, a first inactive part is constituted between the active part and a first end face 12a and a second inactive part between the active part and a second end face 12b. In the first and second inactive parts, notches 17 and 18 are formed on the lower face of the piezoelectric material 12 so that they pass through from one side to the other side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric element used for driving one end of which is fixed to a fixed member and the other end is fixed to a driven member, and a piezoelectric actuator device having the piezoelectric element. The present invention relates to a piezoelectric element and a piezoelectric actuator device using a displacement that expands and contracts in a direction connecting the first end and the other end.

  Conventionally, use of a piezoelectric actuator has been studied for controlling a head for reading a magnetic disk or a magneto-optical disk. For example, Patent Literature 1 below discloses a piezoelectric actuator device shown in a sectional view in FIG.

  In the piezoelectric actuator device 101, a hinge member 104 and a base plate 104A are fixed on a plate 103 that is fixedly provided. The hinge member 104 has a movable part 104a and a fixed part 104b. The movable part 104 a is movable in the surface direction independently of the plate 103.

  The piezoelectric element 105 is bonded and fixed to the movable portion 104 a and the fixed portion 104 b of the hinge member 104 using adhesives 106 and 107.

  A load beam 108 on which a magnetic head (not shown) is mounted is connected to the movable portion 104 a of the hinge member 104. Note that one electrode of the piezoelectric element 105 is connected to the load beam 108 by a silver paste 109.

  By the expansion and contraction of the piezoelectric element 105, the movable portion 104a of the hinge member 104, and thus the magnetic head fixed to the load beam 108 can be moved.

On the other hand, Patent Document 2 below discloses an actuator in which an active portion that is displaced by a piezoelectric effect is arranged at the center in the length direction, and inactive portions are arranged on both sides in the length direction of the active portion. Yes. Here, in the inactive part arranged on one side of the active part, the lower surface of the piezoelectric body is fixed to the fixing member using an adhesive. When a voltage is applied, the active part is displaced, and the piezoelectric body expands and contracts in the length direction. Therefore, the driven member can be moved by moving the end face of the piezoelectric body in the length direction and bringing the end face into contact with the driven member such as a head. Here, bending mode vibration occurs due to the asymmetry of the displacement of the upper and lower surfaces of the piezoelectric body. Therefore, in order to suppress the bending mode vibration, the piezoelectric body is fixed by a portion fixed to the fixing member, that is, an adhesive. A structure is disclosed in which the portion to be separated is as far as possible from the boundary between the active portion and the inactive portion. That is, by reducing the length of the free portion that is not fixed to the fixing member, vibration is reduced by fixing the lower surface side of the piezoelectric body.
JP 2002-184140 A Japanese Patent No. 3347346

  In the conventional piezoelectric actuator device 101, one end portion of the piezoelectric element 105 is fixed to the fixed portion 104b by the adhesive 106, and the other end side is fixed to the movable portion 104a by the adhesive 107.

  That is, the piezoelectric element 105 is fixed at both ends. Therefore, when the piezoelectric element 105 expands and contracts, for example, when the piezoelectric element 105 contracts, the piezoelectric element 105 tends to be bent as schematically shown in FIG. As a result, due to the bending, stress was applied to the fixed portion of the piezoelectric element 105 by the adhesives 106 and 107, and peeling and cracks were liable to occur. That is, there is a problem that cracks and peeling tend to occur in the bonded portion indicated by arrow A in FIG.

  When the displacement amount of the piezoelectric element 105 is increased, the peeling and cracking tend to appear more remarkably.

  On the other hand, in the piezoelectric actuator device described in Patent Document 2, the piezoelectric actuator is fixed to the fixing member with an adhesive at a position separated from the active portion. Therefore, it is possible to suppress the bending mode vibration.

  However, in order to suppress the bending mode vibration, the boundary between the active portion and the inactive portion has to be kept as far as possible from the fixing portion by the adhesive. Therefore, the size of the piezoelectric body inevitably becomes long, and it is difficult to reduce the size of the piezoelectric actuator device.

  An object of the present invention is to provide a piezoelectric element and a piezoelectric actuator device that eliminates the above-mentioned drawbacks of the prior art, does not cause an increase in size, and does not easily cause cracking or peeling of a bonded portion due to vibration.

  According to the present invention, first and second end surfaces, a piezoelectric body having an upper surface, a lower surface, and a pair of side surfaces, and first and second internal electrodes stacked in the piezoelectric body via a piezoelectric layer. The first and second internal electrodes are connected to different potentials, and the portion where the first and second internal electrodes are laminated is an active portion that is displaced by the piezoelectric effect, and the first of the piezoelectric body The first and second inactive portions are formed between the second end face and the active portion, and the lower surface of the piezoelectric body is fixed to the fixing member in the first inactive portion, In the piezoelectric element used to drive the driven member with the lower surface of the piezoelectric body fixed to the driven member in the inactive portion, the piezoelectric body is disposed on the lower surface of the piezoelectric body in the first and second inactive portions. That each notch is formed so as to penetrate from one side of the The symptom, the piezoelectric element is provided.

  In a specific aspect of the piezoelectric element according to the present invention, in the first and second inactive portions, notches are provided on the upper surface of the piezoelectric body so as to penetrate from one side surface to the other side surface of the piezoelectric body. It has been.

  In another specific aspect of the piezoelectric element according to the present invention, the notch is provided in the vicinity of a boundary between the first or second inactive portion and the active portion.

  According to still another specific aspect of the piezoelectric element according to the present invention, the depth of the notch is made smaller than the thickness of the piezoelectric layer between the inner electrode of the outermost layer and the lower surface or the upper surface of the piezoelectric body. ing.

  In still another specific aspect of the piezoelectric element according to the present invention, the piezoelectric body is sandwiched between the internal electrode and the internal electrode so that the piezoelectric body expands and contracts in a direction connecting the first and second end faces. The polarization structure is configured.

  In still another specific aspect of the piezoelectric element according to the present invention, when the piezoelectric element is fixed from the lower surface side of the piezoelectric body, the piezoelectric body is opened so that a part of the notch provided in the inactive portion is opened. The notches are provided to allow the to be fixed.

  In still another specific aspect of the piezoelectric element according to the present invention, the notch is provided so that the piezoelectric body is fixed so that all the openings of the notch are opened.

  In the piezoelectric actuator device according to the present invention, in the first inactive portion of the piezoelectric element according to the present invention, the piezoelectric element is fixed to the fixing member from the lower surface side of the piezoelectric body, and on the second inactive portion side. The lower surface of the piezoelectric body is fixed to the driven member, and the piezoelectric element is fixed to the fixed member and the driven member so that at least a part of the opening of the notch provided in the first and second inactive portions is opened. Has been.

  In the piezoelectric element according to the present invention, in the first and second inactive portions, notches are provided on the lower surface of the piezoelectric body so as to penetrate from one side surface of the piezoelectric body to the other side surface. Even if the piezoelectric body is fixed to the fixing member and the driven member using an adhesive so that at least a part of the opening is opened, the restraining force due to the fixing is relaxed. That is, in the stacked piezoelectric element, the active part is displaced, whereas the inactive part is displaced in accordance with the displacement of the active part. In other words, the inactive portion becomes a constraining layer for the active portion, and acts to suppress displacement of the active portion. Therefore, by providing the notch on the lower surface of the piezoelectric body in the first and second inactive portions, the displacement restraining action by the inactive portions can be reduced. Therefore, it is possible to suppress undesired bending mode vibrations, and it is possible to suppress peeling and cracking of the fixing portion due to the adhesive. Further, reducing the restraining force means that the stress due to the displacement of the active portion is not easily transmitted to the first and second inactive portions, and therefore, the fixing portion is hardly peeled off by the adhesive. Become.

  Since the formation of the notch is characterized by suppressing the peeling of the fixed portion by the adhesive, it is not necessary to lengthen the inactive portion so much in the present invention, which may lead to an increase in size. Absent. Therefore, according to the present invention, it is small, and it is difficult for the fixing part to be peeled off by the adhesive, and even if the adhesive adheres excessively, it is stored in the notch, so that the adhesive is attached to the active part. It is possible to provide a highly reliable piezoelectric element that hardly causes vibration inhibition.

  When a cutout is provided on the upper surface of the piezoelectric body so as to penetrate from one side surface of the piezoelectric body to the other side surface, the vertical symmetry of displacement is enhanced in the first and second inactive portions. The occurrence of bending mode vibrations can be further suppressed.

  In the present invention, it is preferable that a notch is provided in the vicinity of the boundary between the first and second inactive portions and the active portion. In that case, further miniaturization can be achieved.

  When the depth of the notch is smaller than the thickness of the piezoelectric layer between the inner electrode of the outermost layer and the lower or upper surface of the piezoelectric body, the notch does not reach the inner electrode of the outermost layer, so the outermost layer The internal electrode of the layer is not easily broken. Further, since it is not necessary to form a deep notch, the notch can be easily formed.

  When the polarization structure of the piezoelectric layer sandwiched between the internal electrode and the internal electrode is configured so that the piezoelectric body expands and contracts in the direction connecting the first and second end faces, the bending mode is applied according to the present invention. Thus, it is possible to provide a piezoelectric element that is capable of utilizing the expansion and contraction in the length direction connecting the first and second end faces.

  When the piezoelectric element is fixed from the lower surface side of the piezoelectric body, the notch is provided so that the piezoelectric body can be fixed so that a part of the notch provided in the active part opens. According to the present invention, by fixing the piezoelectric body so that a part of the opening is exposed, it is possible to suppress peeling of the fixed portion by the adhesive of the piezoelectric element.

  The piezoelectric element may be fixed with an adhesive so that all of the opening portions of the notch are opened. Even in this case, peeling of the bonded portion can be effectively suppressed due to the presence of the notches.

  In the piezoelectric actuator device according to the present invention, in the first and second inactive portions of the piezoelectric element configured according to the present invention, the piezoelectric element is fixed to the fixing member and the driven member from the lower surface side of the piezoelectric body using an adhesive. The piezoelectric element is fixed to the fixing member and the driven member so that at least a part of the opening of the notch is opened.

  Therefore, in the piezoelectric actuator device, the bending mode vibration is effectively suppressed, and peeling of the fixed portion by the adhesive can be effectively prevented. Therefore, it is possible to provide a highly reliable piezoelectric actuator device that does not cause an increase in size and is difficult to cause separation of a fixed portion by an adhesive.

  In addition, when the piezoelectric body is fixed to the fixing member or the driven member using an adhesive, even if the adhesive is excessively attached, the excess adhesive is accommodated in the notch. Vibration inhibition due to adhesion to the active part is difficult to occur.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1 is a partially cutaway front sectional view for explaining a piezoelectric actuator device according to a first embodiment of the present invention.

  In the piezoelectric actuator device 1, the piezoelectric element 11 is fixed to the fixing member 2 using the adhesive 3 on one end side. The other end side of the piezoelectric element 11 is fixed to the driven member 5 using an adhesive 4. The fixed member 2 is a portion that is fixedly arranged, and the driven member 5 is a member that is driven by the piezoelectric element 11.

  Specifically, the piezoelectric actuator device 1 of this embodiment is used in a magnetic head driving device 6 shown in a plan view in FIG. That is, in the magnetic head driving device 6, the piezoelectric element 11 is fixed so as to straddle the fixed member 2 and the driven member 5 formed of a head support plate with the magnetic head 7 attached to the lower surface. The driven member 5 has a plate shape, and one end side is connected to the fixing member 2 by a pin 8. Therefore, when the piezoelectric element 11 expands and contracts, the driven member 5 is rotated about the pin 8, and the magnetic head 7 attached to the driven member 5 is moved about the pin 8.

  However, the piezoelectric actuator device 1 according to the present invention is not limited to the magnetic head driving device 6 shown in FIG. 2, and is used to drive various driven members.

  Returning to FIG. 1, the piezoelectric element 11 includes a rectangular parallelepiped piezoelectric body 12. The piezoelectric body 12 has a first end surface 12a, a second end surface 12b facing the first end surface, an upper surface 12c, and a lower surface 12d. The direction connecting the first end surface 12a and the second end surface 12b is defined as the length direction.

  In the piezoelectric body 12, a plurality of first internal electrodes 13 and a plurality of second internal electrodes 14 are arranged so as to overlap with each other via a piezoelectric layer. The plurality of first internal electrodes 13 are drawn out to the first end face 12a, and the internal electrodes 14 on the second end face are drawn out to the second end face 12b.

  On the other hand, at the height position where the first internal electrode 13 is formed, a dummy electrode 15 is formed in front of the inner end of the first internal electrode 13 with a gap from the first internal electrode 13. . The dummy electrode 15 is drawn out to the second end face 12b. Similarly, in the portion where the second internal electrode 14 is laminated, the dummy electrode 16 is disposed in front of the second internal electrode 14 with a gap therebetween. The dummy electrode 16 is drawn out to the first end face 12a.

  First and second external electrodes 19 and 20 are formed so as to cover the first end surface 12 a and the second end surface 12 b of the piezoelectric body 12. As described above, the piezoelectric element 11 shown in FIG. 1 can be obtained.

  In the piezoelectric element 11, by applying an alternating electric field between the first and second external electrodes 19 and 20, the piezoelectric element 11 expands and contracts in the length direction. Therefore, in the piezoelectric element 11, the portion where the first and second internal electrodes 13, 14 overlap with each other through the piezoelectric layer constitutes an active portion that is displaced by application of a voltage. A first inactive portion is disposed between the active portion and the first end surface 12a, and a second inactive portion is disposed between the active portion and the second end surface 12b. In the first inactive portion, a notch 17 is formed in the lower surface 12 d of the piezoelectric body 12. In the present embodiment, a notch 17 is arranged near the boundary between the first inactive part and the active part. The second notch 18 is formed in the lower surface 12d of the piezoelectric body 12 in the second inactive portion. In the present embodiment, the second notch 18 is disposed in the vicinity of the boundary between the second inactive part and the active part in the second inactive part.

  Each of the notches 17 and 18 is formed on the lower surface of the piezoelectric body 12 so as to extend from one side surface to the other side surface.

  In the present embodiment, the cross-sectional shape of the notches 17 and 18 is a rectangle, but the cross-sectional shape of the notches 17 and 18 may be an appropriate shape such as a semicircle or a triangle.

  Although the dummy electrodes 15 and 16 are not necessarily provided in the present invention, the number of prepared internal electrode patterns can be reduced by forming the dummy electrodes 15 and 16. This will be described with reference to a method for manufacturing the piezoelectric body 12.

  In obtaining the piezoelectric body 12, the first and second piezoelectric green sheets on which the internal electrode patterns 21 and 22 shown in FIGS. 3A and 3B are printed are alternately laminated. Then, a plain piezoelectric green sheet is laminated on top. In this way, a mother laminate is obtained.

  As shown in FIGS. 4 (a) and (b), the mother laminate 31 obtained as described above is cut along the alternate long and short dash lines X and Y using a dicing saw or the like. A laminate for obtaining the piezoelectric body 12 is obtained. In addition, what is necessary is just to form the below-mentioned notches 17 and 18 previously using the same dicing saw before the cutting | disconnection of the said X and Y direction. That is, after the notches 17 and 18 are formed, cutting in the X direction and the Y direction is performed. In this way, a laminate having notches 17 and 18 can be obtained. By firing the obtained laminate, the piezoelectric body 12 shown in FIG. 1 can be obtained.

  Further, by providing the dummy electrodes 15 and 16, the piezoelectric body 12 can be obtained simply by preparing the two types of internal electrode patterns 21 and 22 shown in FIGS.

  In the manufacturing method described above, the notches 17 and 18 are formed before firing. However, after the individual piezoelectric bodies 12 are obtained, the notches 17 and 18 may be formed using a dicing saw or the like. That is, the notches 17 and 18 may be formed either before firing or after firing.

  As the piezoelectric material constituting the piezoelectric body 12, an appropriate piezoelectric ceramic such as lead zirconate titanate ceramic or lead titanate ceramic can be used. In addition, as a material constituting the internal electrodes 13 and 14 and the external electrodes 19 and 20, an appropriate metal or alloy such as Cu or Ag can be used. As a method of forming the first and second external electrodes 19 and 20, a thin film forming method such as sputtering or vapor deposition, or an appropriate method such as coating / curing or baking of a conductive paste can be used.

  In the piezoelectric element 11, by applying an alternating electric field between the first and second external electrodes 19 and 20, the piezoelectric element 11 expands and contracts in the length direction, which is the direction connecting the first and second end faces 12 a and 12 b. To do. The driven member 5 can be driven and controlled using this expansion / contraction behavior.

  In the piezoelectric actuator device 1 of the present embodiment, when the piezoelectric element 11 is fixed to the fixing member 2 with the adhesive 3, the piezoelectric element 11 is fixed to the fixing member 2 so that at least a part of the opening of the notch 17 is exposed. ing. Similarly, the piezoelectric element 11 is fixed to the driven member 5 on the second inactive part side using the adhesive 4 so that at least a part of the opening of the notch 18 is exposed.

  Therefore, when the piezoelectric actuator device 1 is driven by applying a voltage, since the notches 17 and 18 are provided, the restraining force due to the fixing portion by the adhesives 3 and 4 is reduced, and vibration due to the bending mode occurs. hard. This will be described with reference to FIG. FIG. 5 is a partially cutaway front sectional view schematically showing displacement of the piezoelectric element 11 when the piezoelectric actuator device 1 is driven. When an AC electric field is applied to the piezoelectric element 11, the displacement is repeated between the vibration state indicated by the solid line in FIG. 5 and the vibration state indicated by the broken line.

  As is clear from FIG. 5, since the first and second cutouts 17 and 18 are provided symmetrically on both sides of the active part, the restraining force for the active part is symmetrical on both sides of the active part. Therefore, as shown in FIG. 5, vibration in the bending mode hardly occurs.

  Then, as described above, the fact that the restraining force by the adhesives 3 and 4 is reduced means that the stress applied to the adhesives 3 and 4 due to the displacement of the active portion is reduced. Therefore, even if the piezoelectric element 11 is repeatedly driven, the fixed portion is hardly peeled off by the adhesives 3 and 4.

  In addition, in this embodiment, since the cutouts 17 and 18 are provided, the fixing portion is prevented from being peeled off by the adhesives 3 and 4. In other words, in the piezoelectric element 11, the free end is provided. There is no need to lengthen the length of the part. Therefore, it is possible to provide the piezoelectric actuator device 1 with excellent reliability that is less likely to cause peeling of the fixed portion due to the adhesives 3 and 4 while downsizing.

  In the embodiment shown in FIG. 1, the notches 17 and 18 are provided in the first and second inactive portions, respectively. Also on the top surface 12c of the eleventh piezoelectric body 12, notches 17A and 18A may be formed, respectively. The notches 17A and 18A are formed in the first and second inactive portions, respectively. In FIG. 6, the notch 17A is formed at a position facing the notch 17 on the lower surface side in the thickness direction, and the notch 18A is similarly formed so as to face the second notch 18 in the thickness direction. ing. The notches 17A and 18A are also formed from one side surface to the other side surface.

  As described above, by forming the notches 17A and 18A also on the upper surface side, the symmetry of displacement on the upper surface side and the lower surface side in the piezoelectric element 11 can be improved, which is desirable. In addition, in the piezoelectric element 11A, as is apparent from FIG. 6, the above-described dummy electrode is not formed.

1 is a front sectional view showing a piezoelectric actuator device according to a first embodiment of the present invention. The top view explaining the magnetic head drive device to which the piezoelectric actuator device of the present invention is applied. (A) And (b) is each top view which shows the internal electrode pattern prepared in order to obtain the piezoelectric element shown in FIG. (A) And (b) is the top view and front sectional drawing which show the laminated body of the mother for obtaining the piezoelectric material of the piezoelectric element 11 shown in FIG. The typical partial notch front view which shows the displacement state of the piezoelectric element 11 in the piezoelectric actuator apparatus shown in FIG. The front sectional view showing the modification of the piezoelectric actuator device of the present invention. The partial notch front sectional drawing which shows an example of the conventional piezoelectric actuator apparatus. The typical front view for demonstrating the problem of the conventional piezoelectric actuator apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric actuator device 2 ... Fixed member 3 ... Adhesive 4 ... Adhesive 5 ... Driven member 6 ... Head drive device 7 ... Magnetic head 8 ... Pin 11 ... Piezoelectric element 12 ... Piezoelectric body 12a, 12b ... 1st, 2nd End surface 12c ... Upper surface 12d ... Lower surface 13 ... First internal electrode 14 ... Second internal electrode 15, 16 ... Dummy electrode 17, 18 ... Notch 17A, 18A ... Notch

Claims (8)

A first and second end faces; a piezoelectric body having an upper surface, a lower surface and a pair of side surfaces; and first and second internal electrodes laminated via a piezoelectric layer in the piezoelectric body, The first and second internal electrodes are connected to different potentials, and the portion where the first and second internal electrodes are stacked is an active portion that is displaced by the piezoelectric effect, and the first and second end faces of the piezoelectric body First and second inactive portions are formed between the active portion, the lower surface of the piezoelectric body is fixed to the fixing member in the first inactive portion, and the piezoelectric body in the second inactive portion. In the piezoelectric element used to drive the driven member with the lower surface of the fixed to the driven member,
In the first and second inactive portions, the piezoelectric element is characterized in that a notch is formed in the lower surface of the piezoelectric body so as to penetrate from one side surface of the piezoelectric body to the other side surface.   2. The piezoelectric element according to claim 1, wherein in the first and second inactive portions, notches are provided on the upper surface of the piezoelectric body so as to penetrate from one side surface to the other side surface of the piezoelectric body.   3. The piezoelectric element according to claim 1, wherein the notch is provided near a boundary between the first or second inactive portion and the active portion.   The piezoelectric according to any one of claims 1 to 3, wherein a depth of the notch is smaller than a thickness of the piezoelectric layer between the inner electrode of the outermost layer and the lower surface or the upper surface of the piezoelectric body. element.   The polarization structure of the piezoelectric layer sandwiched between the internal electrode and the internal electrode is configured so that the piezoelectric body expands and contracts in a direction connecting the first and second end faces. The piezoelectric element according to any one of claims.   When the piezoelectric element is fixed from the lower surface side of the piezoelectric body, the notch is provided so that the piezoelectric body can be fixed so that a part of the notch provided in the inactive portion is opened. The piezoelectric element according to any one of claims 1 to 5.   The piezoelectric element according to claim 6, wherein the notch is provided so that the piezoelectric body is fixed so that all the openings of the notch are opened. The first inactive portion of the piezoelectric element according to claim 1, wherein the piezoelectric element is fixed to the fixing member from the lower surface side of the piezoelectric body, and on the second inactive portion side. The lower surface of the piezoelectric body is fixed to the driven member, and the piezoelectric element is fixed to the fixed member and the driven member so that at least a part of the opening of the notch provided in the first and second inactive portions is opened. A piezoelectric actuator device.

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