JP6047316B2 - Piezoelectric actuator - Google Patents

Description

  The present invention relates to a piezoelectric actuator that expands and contracts by application of a voltage.

  A piezoelectric element obtained by laminating an internal electrode and a piezoelectric layer expands and contracts in the stacking direction when a voltage is applied, but a single element has a small amount of displacement. Therefore, a method is known in which a large number of piezoelectric elements are stacked to form a multiple-unit piezoelectric actuator body to obtain a large amount of displacement in total. For example, in Patent Document 1, a device is devised to improve the performance of a multilayer piezoelectric actuator composed of such multiple piezoelectric elements. In this way, the multilayer piezoelectric actuator can obtain a large displacement.

JP 2008-277855 A

  4A and 4B are side views showing a conventional piezoelectric actuator 900. FIG. The multilayered piezoelectric actuator body 910 formed by bonding the piezoelectric elements 912 with an adhesive by the above-described multiple connection is sealed with a metal cap 920 in order to prevent deterioration due to humidity. The uppermost upper surface and the lower lower surface (the upper side is the displacement side and the lower side is the fixed side) of the piezoelectric actuator body 910 in the cap 920 are fixed to the bottom of the cap 920 and the seat 930 by an adhesive or a positioning mechanism, respectively. ing. The piezoelectric actuator body 910 is positioned so that its axis is located at the center of the cap 920.

  FIG. 5 is a plan view showing a conventional piezoelectric actuator body 910. For example, in order for the piezoelectric actuator main body 910 to be displaced by 150 μm or more, it is necessary to multiply the □ 6 mm × 10 mm piezoelectric elements 912 by 10 stages or more. During use, a force of several hundreds of N is applied to the cap 920. However, when the piezoelectric element 912 expands, its central portion 915 is greatly displaced as compared with the surrounding 916. The bonded portion is gradually deformed, and as a result, the entire piezoelectric actuator body 910 is curved.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a piezoelectric actuator that can substantially reduce the risk of bending a multiple-connected piezoelectric actuator body.

  (1) In order to achieve the above object, a piezoelectric actuator of the present invention is a piezoelectric actuator that expands and contracts by application of voltage, and includes a piezoelectric actuator body in which a plurality of piezoelectric elements are stacked in series, and the piezoelectric actuator body. The support winding part mounted around the side surface at a predetermined position in the longitudinal direction, the piezoelectric actuator body and the support winding part are housed inside, and the piezoelectric actuator body is displaced by contacting the tip of the piezoelectric actuator body. A cap that transmits to the outside, and the support winding portion is in contact with the inner side surface of the cap to support the side surface of the piezoelectric actuator main body, and prevents the piezoelectric actuator main body from bending.

  As described above, in the piezoelectric actuator of the present invention, the support winding portion is in contact with the inner side surface of the cap and supports the side surface of the piezoelectric actuator body, thereby preventing the bending of the piezoelectric actuator bodies stacked in series. Thereby, even if the piezoelectric actuator body repeatedly expands and contracts, the bonded portion between the elements does not deform and does not curve.

  (2) Moreover, the piezoelectric actuator of the present invention is characterized in that the support winding portion is an elastic film wound around the side surface of the piezoelectric actuator body. As a result, the support winding portion can be gently fixed around the side surface of the piezoelectric actuator main body by elastic force, so that the displacement of the piezoelectric actuator main body is not hindered by the expansion / contraction difference from the cap.

  (3) Moreover, the piezoelectric actuator of the present invention is characterized in that the support winding portion is formed of an insulating material. As a result, insulation between the cap and the piezoelectric actuator body can be maintained, and short-circuiting of the external electrodes can be prevented.

  (4) Further, the piezoelectric actuator of the present invention is characterized in that the support winding portion is mounted around a protective layer of a piezoelectric element constituting the piezoelectric actuator body. Since the protective layer is a portion that does not expand and contract due to voltage application, the support winding portion is not easily affected by the expansion and contraction, and it is possible to prevent problems such as shifting of the mounting position.

  (5) Further, in the piezoelectric actuator of the present invention, the support winding portion is formed of a resin having heat shrinkability, and is fixed around the side surface of the piezoelectric actuator body by the shrinkage force generated by the heat shrinkability. It is characterized by that. Thereby, the mounting of the support winding portion is facilitated, and the mounting portion is not easily displaced from the mounting location.

  According to the present invention, it is possible to substantially reduce the risk of bending the multiple piezoelectric actuator bodies.

It is a side view which shows the piezoelectric actuator of 1st Embodiment. It is a plane sectional view showing the piezoelectric actuator of a 1st embodiment. It is a side view which shows the piezoelectric actuator of 2nd Embodiment. (A), (b) is a side view which shows the conventional piezoelectric actuator. It is a top view which shows the conventional piezoelectric actuator main body.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

[First Embodiment]
(Configuration of piezoelectric actuator)
FIG. 1 is a side view showing the piezoelectric actuator 100. The piezoelectric actuator 100 expands and contracts when a voltage is applied, and the tip thereof is displaced according to the voltage. For example, the piezoelectric actuator 100 is used in a positioner (positioning device), a mass flow controller, or the like. As shown in FIG. 1, the piezoelectric actuator 100 includes a piezoelectric actuator main body 110, a cap 120 and a seat 130.

  The piezoelectric actuator main body 110 is configured such that a plurality of piezoelectric elements 112 are stacked in a series direction and expand and contract on a straight line (multiple connection). The piezoelectric element 112 is formed by alternately stacking piezoelectric layers and internal electrodes. The piezoelectric actuator main body 110 is formed by bonding a plurality of piezoelectric elements 112 in series in the expansion and contraction direction at the end surfaces. A large displacement can be obtained efficiently by providing multiple piezoelectric elements 112. In the example shown in FIG. 1, the piezoelectric actuator main body 110 is formed by multiplying six piezoelectric elements 112. In this manner, the displacement amount in the case where the piezoelectric element 112 has six stations is obtained from the piezoelectric actuator main body 110.

  The support winding portion 115 is mounted around the side surface at a predetermined position in the longitudinal direction of the piezoelectric actuator main body 110. The support winding portion 115 is in contact with the inner side surface of the cap 120 to support the side surface of the piezoelectric actuator main body 110 and maintains the linear expansion and contraction axis of the piezoelectric actuator main body 110 so as not to be displaced. As a result, even if the piezoelectric actuator main body 110 repeatedly expands and contracts, the bonded portion between the elements is not deformed and is not curved.

  The support winding portion 115 is preferably mounted around the protective layer of the piezoelectric element 112 (a state in which the protective layer is covered at the position of the protective layer in the stacking direction). Since the protective layer does not expand and contract due to voltage application, the support winding portion 115 is not easily affected by the expansion and contraction and can prevent problems such as a shift in the mounting position. The protective layer is a layer that is provided at both ends in the stacking direction of the piezoelectric elements 112 as a processing allowance and is not directly driven without applying a voltage.

  Since the support winding portion 115 has the inner wall of the cap 120 around it, the movement of the piezoelectric element 112 in the direction perpendicular to the expansion / contraction direction is restricted. Thereby, the piezoelectric actuator main body 110 can be held at an appropriate position in the cap 120, and the bending of the piezoelectric actuator main body 110 can be prevented.

  When there is no support winding part 115, the bending of the piezoelectric actuator main body 110 becomes more prominent as the number of multiples increases, but as shown in FIG. 1, it circumscribes the piezoelectric element 112 at an intermediate height, and By providing the support winding portion 115 inscribed in the cap 120, the piezoelectric actuator main body 110 is fixed to the approximate center of the cap 120.

  The cap 120 is made of a metal such as SUS, for example, and has a cylindrical shape with a bottomed opening. On the bottom side, a spherical protrusion 125 for transmitting displacement is provided as the tip of the piezoelectric actuator 100. The cap 120 accommodates the piezoelectric actuator main body 110 and the support winding portion 115 therein, and transmits the displacement of the piezoelectric actuator main body 110 to the outside by the bottom portion contacting the tip of the piezoelectric actuator main body 110. The opening of the cap 120 is fixed to the seat 130, and the lead wire of the piezoelectric element 112 goes out through the seat 130 to seal the inside of the cap 120.

  The seat 130 supports the piezoelectric actuator main body 110, and the cap 120 is fixed thereto. For example, in a positioner or the like, the piezoelectric actuator main body 110 is accommodated with a preload applied between the tip of the cap 120 and the seat 130.

(Support winding part)
FIG. 2 is a plan sectional view showing the piezoelectric actuator 100. The support winding portion 115 is preferably made of an elastic film wound around the side surface of the piezoelectric actuator body 110. Thereby, since the support winding part 115 can gently fix the piezoelectric actuator main body 110 to the periphery of the side surface by an elastic force, the displacement of the piezoelectric actuator 100 is not hindered by a difference in expansion and contraction with the cap 120.

  Moreover, it is preferable that the material of the support winding part 115 is what electrically insulates the cap 120 and the piezoelectric actuator main body 110 from each other. Thereby, a short circuit of the external electrode can be prevented. The supporting winding 115 itself may be a metal part that conducts electricity as long as sufficient insulation can be provided on the inside of the cap 120 or the outside of the piezoelectric element 112.

  From the above, the material of the support winding 115 is preferably an insulating and elastic member such as plastic or resin, and particularly preferably has a structure in which a heat shrinkable tube or the like is wound several times. Examples of the resin include polypropylene and polycarbonate.

  The support winding portion 115 using the heat shrinkable tube is fixed around the side surface of the piezoelectric actuator main body 110 by the shrinkage force generated by the heat shrinkability. Thereby, mounting | wearing of the support winding part 115 becomes easy, and the support winding part 115 becomes difficult to shift | deviate from a mounting location. It is possible to use a hard material other than the heat-shrinkable tube, but in that case, it is necessary to use an adhesive. In that case, although the displacement of the support winding portion 115 can be prevented, the piezoelectric actuator main body 110 can be restrained more than necessary to inhibit expansion and contraction.

  When the support winding portion 115 is formed of a heat-shrinkable tube, the piezoelectric actuator main body 110 is restrained softly from the surroundings, and the material itself has elasticity, so that the expansion and contraction of the piezoelectric actuator main body 110 is not restricted.

  The material that supports the piezoelectric element 112 from the side surface and does not hinder displacement is preferably 1/100 or less of the elastic modulus. When PZT is used for the piezoelectric element 112, its elastic coefficient is about 500 GPa. Therefore, rather than the above-mentioned polypropylene and polycarbonate (elastic modulus of about 2 GPa), etc., fluororesins such as polyolefin, polyvinyl chloride, polyvinylidene fluoride and PFA, PTFE, FEP (elastic modulus 0. 2GPa) is preferable as a material that does not hinder displacement.

(Method for manufacturing piezoelectric actuator)
Next, a manufacturing method of the piezoelectric actuator 100 configured as described above will be described. First, the piezoelectric element 112, the cap 120, and the seat 130 are prepared. The piezoelectric actuator body 110 is manufactured by bonding a predetermined number of piezoelectric elements 112 at the end faces in the stacking direction, connecting them in series (multiple connection), and performing a polarization process.

  Next, the support winding portion 115 is attached to the formed piezoelectric actuator main body 110 and inserted into the cap 120. The support winding part 115 can be formed by, for example, stacking a plurality of heat-shrinkable tubes, winding them at a predetermined position, and applying heat to shrink them.

  Finally, the cap 120 and the seat 130 are fixed, and the hole through which the lead wire is passed is sealed. In this way, the piezoelectric actuator 100 that can prevent bending can be easily manufactured.

[Second Embodiment]
In the above embodiment, one support winding portion 115 is provided at an intermediate position obtained by dividing the entire length of the piezoelectric actuator main body 110 into two portions, but support winding portions may be provided at a plurality of locations. FIG. 3 is a side view showing the piezoelectric actuator 200.

  The piezoelectric actuator 200 is configured in the same manner as the piezoelectric actuator 100 except for the support winding portions 215a and 215b. The piezoelectric actuator 200 is provided with support winding portions 215a and 215b at positions obtained by dividing the entire length of the piezoelectric actuator main body 110 into three equal parts. Thereby, there are a plurality of support portions, and the risk of bending the piezoelectric actuator main body 110 can be further reduced. In addition, when the number of stages of multiple piezoelectric elements 112 increases, it can be divided into four or five.

DESCRIPTION OF SYMBOLS 100 Piezoelectric actuator 110 Piezoelectric actuator main body 112 Piezoelectric element 115 Support winding part 120 Cap 125 Spherical protrusion 130 Seat 200 Piezoelectric actuators 215a and 215b Support winding part

Claims (4)

A piezoelectric actuator that expands and contracts by application of voltage,
A piezoelectric actuator body in which a plurality of piezoelectric elements are stacked in series;
A support winding mounted around the side surface at a predetermined position in the longitudinal direction of the piezoelectric actuator body;
The piezoelectric actuator main body and the support winding portion are housed inside, and a cap that transmits the displacement of the piezoelectric actuator main body to the outside by contacting the tip of the piezoelectric actuator main body,
The support winding part is an elastic film wound around the side surface of the piezoelectric actuator body,
The support winding portion is in contact with the inner side surface of the cap and supports the side surface of the piezoelectric actuator main body to prevent the piezoelectric actuator main body from bending. The piezoelectric actuator according to claim 1 , wherein the support winding portion is made of an insulating material. 3. The piezoelectric actuator according to claim 1, wherein the support winding portion is mounted around a protective layer of a piezoelectric element constituting the piezoelectric actuator main body. The supporting winding portion is formed of a resin having a heat-shrinkable, claim 3 that claim 1, characterized in that fixed by the contraction force generated by the heat-shrinkable around the sides of the piezoelectric actuator body The piezoelectric actuator according to any one of the above.

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