JP2013225613A - Piezoelectric actuator and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator that can prevent buckling even in a state of being preloaded, and a method of manufacturing the same.SOLUTION: An piezoelectric actuator 100 which extends and contracts by application of a voltage includes a piezoelectric actuator body 110 such that a plurality of piezoelectric elements 112 and contact members 117-119 contacting respective ends of the plurality of piezoelectric elements 112 are stacked alternately in a series direction, and fastening force is applied among the contact members 117-119 by a fastening mechanism 115 fastening mutually adjacent contact members 117-119, the piezoelectric elements and contact members contacting each other at three or more points having the center of gravity at points on axes of projection and recessed parts such that the axial direction of the contact is aligned with the extension/contraction direction. Consequently while bearing force is improved by improving brittleness to external force, buckling of the piezoelectric actuator body 110 can be prevented in a state of being preloaded.

Description

  The present invention relates to a piezoelectric actuator that expands and contracts by application of a voltage and a method for manufacturing the same.

  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

  However, the multi-layered piezoelectric actuator body is long, weak against a lateral external force such as dropping, and easily damaged. In addition, since the piezoelectric elements are strongly bonded to each other by an adhesive, if there is even one defective piezoelectric element in the multi-layered piezoelectric actuator body, it is connected to the defective piezoelectric element. All non-defective piezoelectric elements are unusable and the loss tends to increase.

  In response to this, the inventors of the present invention form a piezoelectric actuator body 210 by alternately contacting a plurality of piezoelectric elements 112 and contact members 117 to 119 in series as shown in FIG. Countermeasures have been proposed. However, a piezoelectric actuator used in a positioner or the like is mainly used while preloading a displacement surface. Therefore, in this structure, there is a possibility that bending occurs around the contact member 118 as shown in FIG.

  The present invention has been made in view of such circumstances. A piezoelectric actuator capable of improving brittleness against external force and improving proof stress, and preventing bending at a contact position even in a state where a preload is applied, and a method of manufacturing the same The purpose is to provide.

  (1) In order to achieve the above object, the piezoelectric actuator of the present invention is a piezoelectric actuator that expands and contracts by application of a voltage, and abuts against a plurality of piezoelectric elements and respective end portions of the plurality of piezoelectric elements. The piezoelectric actuator main body is provided with a fastening force applied between the contact members by a fastening mechanism in which members are alternately stacked in series and fastened between the contact members adjacent to each other. It is characterized in that it is made up of three or more points whose center of gravity is the point on the axis of contact between the part and the recess, and the axial direction of the contact coincides with the expansion / contraction direction.

  As described above, the piezoelectric actuator of the present invention forms a piezoelectric actuator body by alternately abutting a plurality of piezoelectric elements and abutting members in a series direction, thereby improving brittleness against external force and improving proof stress. be able to. Moreover, since it has a fastening mechanism and a fastening force is applied between the contact members, it is possible to prevent bending of the piezoelectric actuator body at the contact position even when a preload is applied.

  (2) Moreover, the piezoelectric actuator of this invention is characterized by the said fastening mechanism being comprised with the elastic member. Thereby, fastening force can be easily given between contact members.

  (3) Further, the piezoelectric actuator of the present invention is characterized in that the elastic member is arranged so that a fastening force is applied with the axis of contact as a center of gravity. Thereby, the piezoelectric actuator main body which applied the fastening force with sufficient balance can be comprised, and the prevention effect of the bending in the contact position of a piezoelectric actuator main body can be heightened.

  (4) Moreover, the manufacturing method of the piezoelectric actuator of the present invention is the manufacturing method of the above-described piezoelectric actuator, wherein the plurality of piezoelectric elements and the contact members are alternately stacked, and between the contact members adjacent to each other. The piezoelectric actuator main body is formed by fastening with a fastening mechanism, the step of inserting the formed piezoelectric actuator main body into a cap, and the step of fixing the cap and the seat together. . As a result, it is possible to easily manufacture a piezoelectric actuator capable of preventing the bending at the contact position even when preload is applied, while improving the fragility against external force and improving the proof stress.

  ADVANTAGE OF THE INVENTION According to this invention, the bending in the contact position of a piezoelectric actuator main body can be prevented also in the state which applied the preload, improving the brittleness with respect to external force and improving proof stress.

It is a sectional side view which shows the piezoelectric actuator of this invention. It is the front view, side view, and back view which show the contact member. (A)-(c) It is sectional drawing which shows each scene of the manufacturing process of the piezoelectric actuator of this invention. It is a sectional side view which shows the piezoelectric actuator main body of a comparative example. It is a sectional side view which shows the piezoelectric actuator main body of a comparative example.

  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.

(Configuration of piezoelectric actuator)
FIG. 1 is a side sectional 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 body 110 includes a plurality of piezoelectric elements 112, contact members 117 to 119 and a fastening mechanism 115. The piezoelectric actuator body 110 is formed by alternately stacking a plurality of piezoelectric elements 112 and contact members 117 to 119 in a series direction and fastening the adjacent contact members 117 to 119 with a fastening mechanism 115. The piezoelectric element 112 has convex portions 114 at both ends. The protrusion 114 is a spherical protrusion and is preferably formed of SUS, but may be made of ceramic. The convex portion 114 is preferably formed so that the center of the sphere is positioned on the central axis of the piezoelectric element 112. The contact members 117 to 119 are in contact with the respective end portions of the plurality of piezoelectric elements 112.

  The piezoelectric element 112 may be a single piezoelectric body (fired body) 113 in which piezoelectric layers and internal electrodes are alternately stacked. However, a plurality of such piezoelectric elements 112 are bonded in series at the end faces. It is preferable that A large displacement can be obtained efficiently by forming the piezoelectric element 112 by connecting the piezoelectric bodies 113 in multiples. In the example shown in FIG. 1, the piezoelectric element 112 is formed by multiplying six piezoelectric bodies 113. Thus, the displacement amount by the piezoelectric actuator main body 110 maintains the displacement amount when the piezoelectric body 113 is twelve stations.

  The piezoelectric element 112 is fastened only by contact through the contact member 118. Therefore, even when a defect occurs in any of the plurality of piezoelectric elements 112, only the defective piezoelectric element 112 can be used interchangeably. In the piezoelectric actuator 100, even if a defective product of the piezoelectric body 113 is confirmed in the piezoelectric element 112 on the distal end side, it does not affect the piezoelectric element 112 on the seat side, and the piezoelectric element 112 on the seat side is not reinstated. It can be used.

  In addition, since the length is not increased due to multiple connection, the amount of warpage of the entire piezoelectric actuator 100 can be reduced. There is a variation in parallelism between both end faces of the single piezoelectric body 113, and when they are made into multiples and the portions that are scattered are stacked, warping due to the multiples occurs. The amount of warpage increases as the number of multiples increases, and becomes prominent, resulting in deviation. In the piezoelectric actuator 100, the number of the piezoelectric bodies 113 that are integrally formed in a multiplicity is reduced, and since the contact members 117 to 119 having dimensional accuracy are used, the amount of warpage can be dispersed and the deviation can be reduced. . Further, by shortening the both ends of the piezoelectric element 112 without increasing the length, the moment generated in the piezoelectric element 112 when a certain external force is applied is reduced, and the proof strength against the external force is improved.

  The contact members 117 to 119 are made of, for example, metal and have a recess 116 on at least one main surface. The contact member 117 on the front end side has a recess 116 on the main surface on the seat 130 side, the contact member 118 for linkage has the recess 116 on both main surfaces, and the contact member 119 on the seat side A recess 116 is formed on the main surface on the distal end side. 2A to 2C are a front view, a side view, and a rear view showing the contact member 118 for linking.

  The concave portion is formed as a conical hole, and each contact between the convex portion 114 and the concave portion 116 is made on a circle centered on a point on these axes. It is preferable that the contact is made on a circle, but contact is made at least at three or more points with the center of gravity as the point on the axis of the convex portion 114 and the concave portion 116, and the axial direction of the contact coincides with the expansion / contraction direction. That's fine. By abutting at three or more points, the convex portion 114 does not deviate from a predetermined position in a direction perpendicular to the expansion / contraction direction. Note that the axis of contact is an axis determined from the symmetry of the shape of the convex portion 114 and the concave portion 116.

  Thus, the convex part 114 and the recessed part 116 contact | abut, and it is easy to stack the some piezoelectric element 112 in an appropriate position. Then, the piezoelectric actuator main body 110 is configured by contact, so that the convex portion 114 can slide on the concave portion 116 to release the external force, and the proof stress when the piezoelectric actuator 100 receives the external force is improved. Can do. The force in the expansion / contraction direction of the piezoelectric element 112 can be sufficiently transmitted.

  Since the contact members 117 to 119 have the inner wall of the cap 120 around them, the movement of the piezoelectric element 112 in the direction perpendicular to the expansion / contraction direction is restricted. Thereby, the piezoelectric elements 112 can be stacked at appropriate positions in the cap 120. Further, the piezoelectric actuator main body 110 can be formed by putting the piezoelectric element 112 and the contact members 117 to 119 in the cap 120 in a predetermined order.

  The fastening mechanism 115 fastens between the contact members 117 to 119 adjacent to each other, and applies a fastening force in the compression direction between the adjacent contact members 117 to 119. Accordingly, it is possible to prevent the piezoelectric actuator body 110 from being bent at the contact position even when a preload is applied to the piezoelectric actuator 100.

  The fastening mechanism 115 is preferably composed of an elastic member such as a spring. Thereby, a fastening force can be easily given between the contact members 117-119. In the case where an elastic member is provided as the fastening mechanism 115, it is preferable that the fastening mechanism 115 be arranged so that a fastening force is applied with the axis of contact as the center of gravity.

  Thereby, the piezoelectric actuator main body 110 to which the fastening force is applied in a balanced manner can be prepared, and the effect of preventing the bending at the contact position of the piezoelectric actuator main body can be enhanced. For example, if three or more springs are provided equally on the peripheral edge portions of the contact members 117 to 119, it becomes easy to adjust the parallelism of the contact members 117 to 119.

  The spring constant of the elastic member is sufficient to prevent bending at the contact position if a fastening force of 280 N or more is obtained between adjacent contact members 117 to 119 in a product such as a mass flow controller on which the piezoelectric actuator 100 is mounted. Have proven to be effective. On the other hand, if the fastening force is too large, it is difficult to fasten the adjacent contact members 117 to 119 with the piezoelectric element 112 sandwiched therebetween, and therefore the fastening force is preferably 400 N or less. In this manner, the type of elastic member and the spring constant can be designed in consideration of the number of elastic members to be used and the required fastening force.

  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 inside, the opening is fixed to the seat 130, and the lead wire of the piezoelectric element 112 is taken out through the seat 130 so that the inside of the cap 120 is sealed. The cap 120 is provided with a bellows 128 so that the tip can be displaced according to the expansion and contraction of the piezoelectric actuator main body 110. Instead of the bellows 128, the tip of the cap 120 may have a diaphragm structure.

  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 100 is installed with a preload applied between the tip of the cap 120 and the seat 130.

(Method for manufacturing piezoelectric actuator)
Next, a manufacturing method of the piezoelectric actuator 100 configured as described above will be described. 3A to 3C are cross-sectional views showing scenes of the manufacturing process of the piezoelectric actuator. First, the piezoelectric element 112, the contact members 117 to 119, the cap 120, and the seat 130 are prepared. The piezoelectric element 112 is manufactured by bonding a predetermined number of piezoelectric bodies 113 at the end faces in the stacking direction and connecting them in series (multiple connection), providing convex portions 114 at both ends, and performing polarization treatment.

  Next, a plurality of piezoelectric elements 112 and contact members 117 to 119 are alternately stacked, and the adjacent contact members 117 to 119 are fastened by the fastening mechanism 115 to form the piezoelectric actuator body 110. At this time, the convex portion 114 and the concave portion 116 are fitted and contact each other. In that case, it is efficient if the contact member 117 and the contact member 118 are fastened first, and then the contact member 118 and the contact member 119 are fastened separately. The piezoelectric actuator main body 110 formed in this way is inserted into the cap 120.

  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, it is possible to easily manufacture the piezoelectric actuator 100 that can prevent the bending at the contact position even when the preload is applied, while improving the brittleness against external force and improving the proof stress.

  When the piezoelectric actuator main body 110 is formed, the contact members 117 to 119 and the piezoelectric element 112 are merely in contact with each other, and are not fastened as an integral system with an adhesive or the like. Therefore, if the seal between the cap 120 and the seat 130 of the piezoelectric actuator 100 is released and the piezoelectric actuator main body 110 is taken out and separated, the cap 120 can be disassembled into the piezoelectric element 112 and the contact members 117 to 119.

(Other embodiments)
The piezoelectric actuator main body 110 may be composed of three or more piezoelectric elements. At the time of designing, it is preferable that the number of piezoelectric bodies 113 constituting the piezoelectric actuator main body is constant, and the final displacement obtained is designed to be constant.

  Moreover, the recessed part 116 of the contact members 117-119 may be formed in shapes other than a conical hole, if it is a shape which has a central axis and becomes narrow toward a bottom part. Examples of the shape of the hole include a regular triangular pyramidal hole, an elliptical pyramidal hole, and a trapezoidal hole.

  Further, the convex portion 114 of the piezoelectric element 112 may be formed in a shape other than a spherical shape such as an ellipsoid. In that case, it is preferable that the convex portion 114 has a shape having a point on the central axis of the piezoelectric element 112 as a center of gravity.

  Further, the concave portion 116 may be provided in the piezoelectric element 112, and the convex portion 114 may be provided in the contact members 117 to 119. In this case, it is difficult to constrain the contact portion with the inner wall surface of the cap 120. However, the contact member for fastening may be a sphere, and there is a possibility that an advantage of easy manufacture can be obtained.

DESCRIPTION OF SYMBOLS 100 Piezoelectric actuator 110 Piezoelectric actuator main body 112 Piezoelectric element 113 Piezoelectric body 114 Convex part 115 Fastening mechanism 116 Concave part 117-119 Contact member 120 Cap 125 Spherical protrusion 128 Bellows 130 Seat

Claims (4)

A piezoelectric actuator that expands and contracts by application of voltage,
A plurality of piezoelectric elements and contact members that contact the respective end portions of the plurality of piezoelectric elements are alternately stacked in a series direction, and a fastening mechanism that fastens the contact members adjacent to each other is provided between the contact members. A piezoelectric actuator body to which a fastening force is applied,
The piezoelectric actuator is characterized in that the contact is made at three or more points with a center on the point of contact between the convex part and the concave part, and the axial direction of the contact coincides with the expansion / contraction direction.   The piezoelectric actuator according to claim 1, wherein the fastening mechanism is made of an elastic member.   The piezoelectric actuator according to claim 2, wherein the elastic member is arranged so that a fastening force is applied with the axis of contact as a center of gravity. A method for manufacturing a piezoelectric actuator according to any one of claims 1 to 3,
A step of alternately stacking the plurality of piezoelectric elements and contact members, and fastening the contact members adjacent to each other by a fastening mechanism to form the piezoelectric actuator body;
Inserting the formed piezoelectric actuator body into a cap;
And a step of fixing the cap and the seat to each other.

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