JP2020035972A - Piezoelectric actuator - Google Patents

Abstract

To provide a piezoelectric actuator which can be used even in a severe environment, and can accurately detect a displacement without restricting the displacement of a piezoelectric element.SOLUTION: A piezoelectric actuator includes: a piezoelectric actuator body 105 formed of a plurality of piezoelectric elements 110 connected in series; a transfer body 150 which has a body part 152 which continuously connects between at least two fastening parts 151 and 151 which are respectively fastened to positions between piezoelectric elements 110 mutually apart in the displacement direction of the piezoelectric actuator body 105, to transmit the displacement between the two fastening parts 151; a displacement sensor 155 which detects the transferred displacement; a seat 140 which fixes one end of the piezoelectric actuator body 105; a cap 160 which is formed in a bottomed cylindrical shape, internally houses the piezoelectric actuator body 105, the transfer body 150 and the displacement sensor 155, and has an opening end sealed on the seat. The displacement sensor 155 is attached to the transfer body 150.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric actuator that is displaced by applying a voltage.

  A piezoelectric element constituting a piezoelectric actuator exhibits hysteresis in the process of expansion and contraction. Therefore, in precision positioning applications used for manufacturing semiconductors and high-definition liquid crystals, feedback control is performed by a displacement sensor to reduce positioning errors due to hysteresis. Further, the piezoelectric actuator is also used as a flow control valve for precisely supplying various gases to a semiconductor manufacturing apparatus or a fine movement mechanism of a precision numerical control processing machine. Also, with the advancement of control of medical manipulators and attitude control of aerospace vehicles, use of piezoelectric actuators that can be controlled with high precision is being studied.

  In feedback control of a piezoelectric actuator, an external sensor for detecting displacement is often used. When such a feedback control method is applied, high-precision positioning is possible, but the system is complicated and expensive, and its use is limited. On the other hand, a simple feedback control using a partial displacement signal by directly attaching a displacement sensor such as a strain gauge to a resin-sealed piezoelectric actuator body has been proposed (see Patent Document 1).

JP-A-5-206536

  However, in the piezoelectric actuator described in Patent Document 1, although a simple sealing is performed, when a strain gauge, which is a relatively inexpensive displacement sensor, is used in a severe environment such as under high humidity or corrosive gas. In addition, deterioration of its characteristics is inevitable, and stable use over a long period of time is difficult. Further, if the displacement sensor is directly attached to the piezoelectric element, the displacement of the piezoelectric element is partially restrained, which causes a crack in the piezoelectric element and causes dielectric breakdown.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a piezoelectric actuator that can be used in a severe environment and that can accurately detect displacement without restricting displacement of a piezoelectric element. I do.

  (1) In order to achieve the above object, a piezoelectric actuator according to the present invention is a piezoelectric actuator that is displaced by applying a voltage, and includes a piezoelectric actuator body formed by connecting a plurality of piezoelectric elements in series, At least two fixing portions respectively fixed at positions between the piezoelectric elements that are separated from each other in the displacement direction of the actuator body, continuously connect the fixing portions, and transmit the displacement between the two fixing portions. A transmitting body having a main body portion, a displacement sensor for detecting the transmitted displacement, a seat for fixing one end of the piezoelectric actuator main body, a bottomed cylindrical shape, and the inside of the piezoelectric actuator main body, the A cap accommodating the transmission body and the displacement sensor, and having an open end sealed to a seat, wherein the displacement sensor is attached to the transmission body. It is characterized in that.

  As described above, since the displacement sensor is not directly attached to the surface of the piezoelectric element parallel to the direction of displacement, the displacement can be detected via the transmission body without restricting the displacement of the piezoelectric element. As a result, the displacement amount of the piezoelectric actuator main body can be detected while preventing the dielectric breakdown due to the crack due to the displacement constraint, and the positioning error when performing the positioning using the piezoelectric actuator can be reduced. In addition, the cap can protect the piezoelectric actuator body and the displacement sensor from the surrounding environment, and can improve the reliability and durability of the piezoelectric actuator.

  (2) In the piezoelectric actuator of the present invention, the transmitting body is formed of a U-shaped thin plate, and both bent front ends of the U-shaped thin plate are fixed to the piezoelectric actuator body as the fixing portions. It is characterized by having. By using both bent end portions in this way, the transmitter is sufficiently fixed without directly attaching the displacement sensor to the surface parallel to the displacement direction of the piezoelectric element, and the displacement sensor is The strain applied to the sensor is averaged, and the durability of the displacement sensor can be improved.

  (3) In the piezoelectric actuator according to the aspect of the invention, the length of the main body, which is a central portion between the fixing portions of the thin plate, in the displacement direction may be between the fixing portions fixed to the piezoelectric actuator. It is longer than the linear distance in the displacement direction, and the main body is arranged to be bent by a compressive force between the two fixing portions. Accordingly, when the piezoelectric actuator main body is displaced, particularly, when the piezoelectric actuator main body is extended, the transmission body that is previously bent is also moved in a direction in which the bending is canceled in accordance with the displacement of the piezoelectric actuator main body. In addition, the piezoelectric actuator main body is not restricted by the transmission body. Therefore, the occurrence of cracks and the like in the piezoelectric element can be suppressed, and the displacement can be stably transmitted to the displacement sensor.

  (4) The piezoelectric actuator according to the present invention is characterized in that the main body is a flat plate that does not resonate with the displacement of the piezoelectric actuator main body. Thereby, the response to displacement can be improved. The shape that does not resonate with the displacement of the piezoelectric actuator main body indicates that the main body is formed in a shape that takes into account the resonance of the main body with respect to the displacement of the piezoelectric actuator main body. For example, the main body may be trapezoidal or irregular.

  (5) Further, in the piezoelectric actuator of the present invention, the pair of U-shaped thin plates are provided in parallel with respect to the displacement direction, and the displacement sensor includes at least one of the pair of U-shaped thin plates of the main body. It is characterized in that the parts are connected to each other. Thus, when the bending of the main body of each thin plate is deformed, the displacement of the piezoelectric actuator can be detected by changing the distance between the points where the pair of thin plates are connected by the displacement sensor.

  (6) The piezoelectric actuator according to the present invention is characterized in that the fixing portion is fixed to the piezoelectric actuator main body within a range in which an active region of the piezoelectric element is projected in a displacement direction. Thus, the displacement can be detected without restricting the stress generated between the inactive region and the active region.

  (7) The piezoelectric actuator according to the present invention is characterized in that the main body has a reinforcing portion extending in a direction parallel to the displacement direction. Thereby, the rigidity of the main body is improved, and the responsiveness of the displacement sensor can be improved. The reinforcing portion may have a rib structure, for example, by bending an outer edge portion of a main body portion of the transmission body in a direction parallel to a displacement direction of the piezoelectric actuator main body, or a ceramic thin plate of alumina, zirconia, or the like may be attached to the main body portion. It can be formed by attaching.

  (8) The piezoelectric actuator according to the present invention is characterized in that the fixing portion is fixed to both end faces of one of the plurality of piezoelectric elements. Thus, the length of the main body between the fixing portions can be minimized, and the responsiveness of the displacement sensor can be improved. Even in this case, by multiplying the measured displacement amount by the number of piezoelectric elements provided in the piezoelectric actuator main body, the displacement amount of the entire piezoelectric actuator can be obtained.

  (9) Further, in the piezoelectric actuator according to the present invention, the fixing portion is fixed to both end surfaces of an element connected body to which two or more piezoelectric elements of the plurality of piezoelectric elements are connected, and the main body section Is characterized by being disposed over two or more piezoelectric elements between the fixing portions. Thereby, a large variation due to the plurality of piezoelectric elements can be measured, and the measurement accuracy is improved. Also, a signal closer to the displacement of the entire piezoelectric actuator can be obtained than when measuring the displacement between one piezoelectric element. Further, the displacement amounts of the plurality of piezoelectric elements can be measured by the displacement sensor, and the number of piezoelectric elements on which the displacement sensors are not disposed can be reduced. Therefore, it is possible to reduce a positioning error caused by a change in the amount of displacement of the piezoelectric element where the displacement sensor is not disposed.

  (10) Further, the piezoelectric actuator of the present invention is characterized in that one of the driving terminals of the piezoelectric actuator body and one of the detecting terminals of the displacement sensor are common. As a result, when the displacement sensor is housed in the cap, the total number of terminals pulled out from the seat is prevented from increasing, and the structure in which the displacement sensor is housed in the cap has improved environmental resistance. Can be.

(11) The piezoelectric actuator according to the present invention is characterized in that a difference between a thermal expansion coefficient of the transmission body and a thermal expansion coefficient of the piezoelectric element is 10 × 10 ⁻⁶ / ° C. or less. Thereby, a shift in the output of the displacement sensor due to a temperature change can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, it can be used also in a severe environment, and can detect displacement accurately without restricting displacement of a piezoelectric element.

2A and 2B are a front sectional view and a side sectional view showing the piezoelectric actuator of the first embodiment, respectively. (A), (b) It is the front sectional view and bottom view of a seat and a terminal, respectively. It is a front sectional view of a piezoelectric element. It is a perspective view of the transmission body of 1st Embodiment. It is a schematic diagram of a displacement control system. It is a perspective view of a transmission body of a 2nd embodiment. (A), (b) It is the front sectional view and side sectional view which show the piezoelectric actuator of 3rd Embodiment, respectively. It is a perspective view of one of a pair of thin plates which comprise the transmission body of 3rd Embodiment.

  Next, embodiments of the present invention will be described with reference to the drawings. To facilitate understanding of the description, the same reference numerals are given to the same components in each of the drawings, and redundant description will be omitted.

[First embodiment (curved type)]
(Configuration of piezoelectric actuator)
1A and 1B are a front sectional view and a side sectional view showing the piezoelectric actuator 100, respectively. 2A and 2B are a front sectional view and a bottom view of the seat 140 and the terminals 126, 127, and 159, respectively. Note that the piezoelectric actuator 100 shown in the reference diagram is an example, and the present invention is not limited by the number of elements or the like.

  The piezoelectric actuator 100 includes a piezoelectric actuator main body 105, driving terminals 126 and 127, sensor terminals 159, a seat 140, a transmitter 150, a displacement sensor 155, and a cap 160, and expands and contracts by applying a voltage. The piezoelectric actuator 100 is used for, for example, a valve opening / closing control unit of a mass flow controller or a stage driving unit of a precision positioning device. In this case, the piezoelectric actuator 100 displaces a driven body (valve, stage).

  When a voltage is applied to the pair of external electrodes 116 and 117 via the pair of lead wires 121 and 122, each piezoelectric element 110 expands and contracts, and thus the tip of the piezoelectric actuator body 105 is displaced. The driving terminals 126 and 127 are connected to the leads 121 and 122 of the piezoelectric actuator main body 105, and transmit the applied voltage to the leads 121 and 122.

  The seat 140 is adhered to an end of the piezoelectric actuator main body 105, fixes one end thereof, and supports the piezoelectric actuator main body 105. Then, the protrusion 130 on the distal end side is displaced by the expansion and contraction of the piezoelectric actuator body 105 to which the end on the seat 140 side is fixed.

  The seat 140 seals the piezoelectric actuator body 105 by being fixed to the end of the cap 160. Reliability and durability can be improved by adopting a structure in which the piezoelectric actuator body 105 and the displacement sensor 155, which are susceptible to humidity and corrosive gas, are hermetically sealed with a low-humidity inert gas. For example, when used in precision processing machines in which the displacement device gets wet with cutting water, or in piezoelectric valves that control the flow rate of corrosive gas, the positioning accuracy using the piezoelectric actuator is insufficient with open control, and the displacement sensor It is effective to perform positioning or the like by using a piezoelectric actuator capable of performing feedback control.

  In this way, the sealing allows the piezoelectric actuator 100 to operate without any problem even in a severe environment such as under a high humidity or corrosive gas. Since the inside of the cap 160 has a completely airtight structure, it can be used even in an environment where the durability of the piezoelectric element such as humidity and corrosive gas and the displacement sensor is impaired, which leads to an expanded use.

  The terminals 126, 127, and 159 are provided through the seat 140 as hermetic terminals. The through-hole is filled with resin or glass, and is insulated and sealed. The terminals 126, 127, 159 are preferably arranged on the seat 140 around the central axis of the piezoelectric actuator 100 for the displacement sensor and the drive, respectively. As a result, the terminals 126, 127, and 159 can be easily electrically connected.

  It is preferable that one of the driving terminals 126 and 127 of the piezoelectric actuator main body 105 and one of the detection terminals of the displacement sensor 155 be common. For example, a common GND terminal can be used. Thus, when the displacement sensor is housed in the cap, the total number of terminals pulled out from the seat is suppressed from increasing, and it is easy to adopt a configuration in which the displacement sensor is housed in the cap and has improved environmental resistance. it can. Note that terminals separated from each other may be used without using a common terminal.

  The cap 160 has a cylindrical shape with a bottom and an open end, and is formed of metal. The cap 160 accommodates the piezoelectric actuator main body 105 therein while closely contacting the piezoelectric actuator main body 105 in the laminating direction, and has an open end joined to the seat 140 to seal the inside of the cap 160. Thereby, the piezoelectric actuator 100 is protected, and the durability is improved.

  The cap 160 has a diaphragm in which the protrusion 130 abuts on a dome-shaped portion at the tip of the cap. The straight pipe portion of the cap 160 is formed in a cylindrical shape from the center to the bottom of the cap 160. The diaphragm is formed in a dome shape. The cap 160 is preferably made of a material having excellent spring properties such as SUS316 and SUS316L. The base fixes the seat 140, and the seat 140 supports an end of the piezoelectric actuator body 105. When the tip of the cap 160 contacts the driven body, the displacement is transmitted from the piezoelectric actuator 100 to the driven body.

  Inside the cap 160, in addition to the piezoelectric actuator body 105, a transmission body 150 and a displacement sensor 155 are also housed. The cap 160 can protect the piezoelectric actuator body 105 and the displacement sensor 155 from the surrounding environment.

  On the other hand, as shown in FIGS. 1A and 1B, in the piezoelectric actuator 100, a displacement sensor 155 is arranged inside a cap 160, and a sensor terminal 159 is provided on a seat 140. As a result, the piezoelectric actuator 100 including the displacement sensor 155 can receive a displacement signal of the piezoelectric element 110 via the sensor terminal 159. Details of the transmission body 150 and the displacement sensor 155 will be described later.

(Piezoelectric actuator body)
The piezoelectric actuator main body 105 includes a piezoelectric element 110, lead wires 121 and 122, and a projection 130. The plurality of piezoelectric elements 110 constituting the piezoelectric actuator body 105 are arranged and connected in series (multiple connection), and their end faces are bonded with an adhesive. A large displacement can be ensured by bonding the plurality of piezoelectric elements 110. Note that “series” means the direction of expansion and contraction, that is, the direction in which the piezoelectric layers and the internal electrodes in the piezoelectric element 110 are stacked.

  The lead wires 121 and 122 connect the driving terminals 126 and 127 and the external electrodes 117 of the respective piezoelectric elements 110. The connection is made in the same manner on the side opposite to the side surface shown in FIG.

  The protrusion 130 is formed in a hemispherical shape with an inorganic material, and is provided on the distal end side of the piezoelectric actuator body 105 that transmits a displacement to a driven body. The protrusion 130 and the piezoelectric actuator main body 105 are firmly bonded to each other, and the protrusion 130 contacts the inner portion of the cap 160 in the dome shape.

(Piezoelectric element)
FIG. 3 is a front sectional view of the piezoelectric element 110. The piezoelectric element 110 outputs displacement in response to an applied voltage, and has a piezoelectric layer 113, internal electrodes 114 and 115, and external electrodes 116 and 117. In the piezoelectric element 110, piezoelectric layers 113 and internal electrodes 114 and 115 are alternately stacked. Further, on the side surface of the piezoelectric element 110, the external electrodes 116 and 117 are connected to the internal electrodes 114 and 115. The piezoelectric layer can be composed of a piezoelectric material such as PZT or barium titanate. Ag, Ag-Pd, Pt, or the like can be used as the electrode material.

(Transmitter)
FIG. 4 is a perspective view before the transmission body 150 is assembled. The transmission body 150 transmits the displacement of the piezoelectric actuator body 105 to the displacement sensor 155. Since the displacement is transmitted to the displacement sensor 155 via the bending of the transmission body 150, the displacement of the piezoelectric element 110 is not restricted. Therefore, it is possible to prevent dielectric breakdown of the piezoelectric element due to displacement constraint when the displacement sensor is directly attached. In particular, in the case of a large displacement type piezoelectric element or a piezoelectric element used at a high temperature, cracks tend to occur due to the piezoelectric element itself being restrained by a displacement sensor or the like. The piezoelectric actuator 100 can prevent such cracks from occurring, and can improve reliability.

  The transmission body 150 includes at least two fixing portions 151 and a main body 152. The fixing portions 151 are fixed at positions between the piezoelectric elements of the piezoelectric actuator body 105 that are separated from each other in the displacement direction. The main body 152 continuously connects the fixing portions 151 and transmits a displacement between the two fixing portions 151.

  As shown in FIG. 4, it is preferable that the transmission body 150 is formed of a U-shaped thin plate, and both bent end portions of the U-shaped thin plate are fixed to the piezoelectric actuator main body 105 as fixing portions 151. In this case, the U-shape indicates that there is a fixed surface perpendicular to the displacement direction and a uniform surface connecting the fixed surface and the displacement sensor 155.

  Sufficient fixation becomes possible by using such both end portions. In the example shown in FIG. 4, the main body 152 forms a central portion between the thin plate fixing portions 151. The length of the main body 152 in the displacement direction is longer than the linear distance in the displacement direction between the fixing portions 151 fixed to the piezoelectric actuator main body 105, and the main body 152 is bent by the compressive force between the two fixing portions 151. Preferably, they are arranged. For example, a main body that is 0.2 to 2% longer than the length of the piezoelectric element is bent and assembled, and the displacement sensor 155 is attached. Accordingly, when the piezoelectric actuator main body is displaced, particularly, when the piezoelectric actuator main body is extended, the transmission body that is previously bent is also moved in a direction in which the bending is canceled in accordance with the displacement of the piezoelectric actuator main body. In addition, the piezoelectric actuator main body is not restricted by the transmission body. Therefore, generation of cracks and the like in the piezoelectric element can be suppressed, and the displacement can be stably transmitted to the displacement sensor 155.

  The fixing portion 151 is preferably fixed to the piezoelectric actuator main body 105 within a range (a region 151a in the example of FIG. 4) in which the active region of the nearest piezoelectric element 110 is projected in the displacement direction. Thus, the displacement can be detected without restricting the stress generated between the inactive region and the active region. The active region here is a region where the internal electrodes 114 and 115 formed in the piezoelectric element 110 overlap when viewed from the displacement direction. The inactive region is a region in the piezoelectric element 110 excluding the active region.

  The fixing portions 151 are fixed to both end surfaces of one piezoelectric element 110. Thus, the length of the main body between the fixing portions can be minimized, and the responsiveness of the displacement sensor can be improved. Even in this case, by multiplying the measured displacement amount by the number of piezoelectric elements provided in the piezoelectric actuator main body, the displacement amount of the entire piezoelectric actuator can be obtained. In addition, it is possible to adjust the length between the fixing portions 151 according to the amount of displacement required for detection. By making the transmitting body 150 straddle a plurality of piezoelectric elements, a signal reflecting the entire displacement state of the piezoelectric actuator body 105 can be obtained. Thus, the displacement can be detected for a length close to the entire length of the piezoelectric actuator main body 105. Further, the displacement amount of the plurality of piezoelectric elements can be measured by the displacement sensor, and the number of piezoelectric elements on which the displacement sensors are not arranged can be reduced. Therefore, it is possible to reduce a positioning error caused by a change in the amount of displacement of the piezoelectric element where the displacement sensor is not disposed.

  In order to accurately transmit the displacement of the piezoelectric actuator 100 to the displacement sensor 155, a material having high rigidity and close to the thermal expansion of the piezoelectric element 110 is preferably used for the transmission body 150. For example, metal such as stainless steel or invar, or a member formed by joining these with a ceramic thin plate such as alumina or zirconia is preferable.

By selecting a material having a coefficient of thermal expansion close to that of the piezoelectric element 110 for the transmitter 150, an output error due to a temperature change can be suppressed. For example, the difference between the thermal expansion coefficient of the transmission body 150 and the thermal expansion coefficient of the piezoelectric element 110 is preferably 10 × 10 ⁻⁶ / ° C. or less. Accordingly, it is possible to suppress a shift in output between the piezoelectric element 110 and the transmission body 150 due to a temperature change. When it is desired to accurately measure the displacement, the displacement may be corrected by measuring the thermal expansion of the transmission body 150 and the piezoelectric element 110.

(Displacement sensor)
The displacement sensor 155 is formed of, for example, a strain gauge, is attached to the transmission body 150, and detects a displacement transmitted from a part of the piezoelectric actuator body 105. As described above, since the displacement sensor 155 is attached to the piezoelectric actuator main body 105 via the transmission body 150, stress concentration due to direct adhesion to the piezoelectric element and restraint of displacement of the piezoelectric element do not occur. Good durability can be maintained even with a piezoelectric actuator such as a displacement type or a high-temperature type that exhibits a larger displacement than a standard product.

  The displacement sensor 155 is connected to the displacement sensor main body 156 and the lead wires 157 and 158, and the detected displacement is transmitted by connecting the lead wire 158 to the sensor terminal 159. Accordingly, the displacement of the piezoelectric actuator body 105 can be confirmed, and the displacement can be accurately grasped, and precise positioning using the piezoelectric actuator can be performed by feedback control.

(Displacement control system)
The displacement control system 190 can be configured using the piezoelectric actuator 100 described above. FIG. 5 is a schematic diagram of the displacement control system 190. As shown in FIG. 5, the displacement control system 190 includes a piezoelectric actuator 100, a feedback control device 170, and a drive power supply 180.

  The sensor terminal 159 of the displacement sensor 155 is connected to the feedback control device 170. The detected displacement signal is input to the feedback control device 170, which converts the detected signal into a displacement of the piezoelectric actuator 100, and calculates a necessary drive amount based on the detected displacement. I do. The conversion from the detection signal to the displacement is in the opposite phase, and when a contraction signal is input from the displacement sensor 155, the contraction signal is converted into an extension displacement of the piezoelectric actuator 100 and output. Note that the conversion from the detection signal to the displacement is in phase, and when an extension signal is input from the displacement sensor 155, the extension displacement of the piezoelectric actuator 100 is output. The feedback control device 170 controls the drive power supply 180 according to the calculated drive amount, and the drive power supply 180 applies a voltage received from the feedback control device 170 to the piezoelectric actuator body 105. Thus, the displacement control system 190 with reduced errors can be realized.

(Method of manufacturing piezoelectric actuator)
Next, a method of manufacturing the piezoelectric actuator 100 configured as described above will be described. First, a piezoelectric element 110 in which piezoelectric layers and internal electrodes are alternately stacked is manufactured. Specifically, an electrode paste such as Ag or Ag-Pd is printed on a green sheet of piezoelectric ceramics, laminated, pressed, and fired. Next, external electrodes 116 and 117 connected to the internal electrodes are formed on the side surfaces of the piezoelectric element 110 along the laminating direction. The external electrodes 116 and 117 can be formed by printing and firing an electrode paste on the side surface of the piezoelectric element 110. On the other hand, a transmitting body 150 is prepared in which the length of the main body 152 is 1% longer than the length of the piezoelectric element 110 and both ends bent from the end of the main body 152 are the fixing portions 151.

  An adhesive such as epoxy is applied to and adhered to the end faces in the stacking direction of the plurality of obtained piezoelectric elements 110 and connected in series. At this time, the transmitter 150 is bonded to both end faces of the piezoelectric element 110 whose displacement is to be monitored. At that time, only the projected area in the displacement direction of the active area of the nearest piezoelectric element is bonded. At this time, only the projection region of the active region of the piezoelectric element in the displacement direction is bonded. In this way, multiple connection is performed and the adhesive is cured. Then, the metal-made plate-shaped lead wire is fixed to the external electrode, and the multiple piezoelectric actuator body 105 can be manufactured.

  The piezoelectric actuator main body 105 is set on the seat 140, and is covered with a cap 160 and sealed. At this time, the transmitter 150 and the displacement sensor 155 are provided in the piezoelectric actuator main body 105 sealed in the cap 160 of the piezoelectric actuator 100, and the piezoelectric actuator main body 105 is sealed in the cap 160 together with the piezoelectric actuator main body 105. The lead wires 121, 122, 158 connected to the terminals of the displacement sensor 155 and the driving electrodes are connected to the terminals 126, 127, 159 inserted into the seat 140. Thus, the piezoelectric actuator 100 can be manufactured. The drive terminals 126 and 127 are electrically connected to the drive power supply 180, and the sensor terminal 159 is electrically connected to the feedback control device 170.

[Second embodiment (trapezoid or irregular shape)]
In the above-described embodiment, the transmission body 150 is formed by bending a rectangular thin plate into a U-shape, but may have another shape to prevent resonance. FIG. 6 is a perspective view of the transmission body 250. The transmission body 250 includes two fixing portions 251 and a main body 252. The main body 252 is preferably a flat plate that does not resonate with the displacement of the piezoelectric actuator main body 105. In the example shown in FIG. 6, the main body 252 is formed in a trapezoidal shape. Thereby, resonance of the transmission body 250 with respect to the displacement of the piezoelectric actuator body 105 can be prevented, and the response to the displacement can be improved. The central portion of the transmission body 150 may be formed in an irregular shape other than the trapezoid.

[Third embodiment]
In the above embodiment, the transmission body 150 is formed using one thin plate, but the transmission body 350 may be configured using two thin plates. FIGS. 7A and 7B are a front sectional view and a side sectional view showing the piezoelectric actuator 300, respectively. FIG. 8 is a perspective view of one of a pair of thin plates constituting the transmission body 350.

  In the piezoelectric actuator 300, the transmission body 350 has a pair of U-shaped thin plates provided symmetrically and in parallel to the displacement direction. The U-shaped thin plate includes a fixing portion 351 and a main body 352. The fixing portions 351 are fixed to the piezoelectric actuator body 105 at positions between the piezoelectric elements 110 which are separated from each other in the displacement direction. A fold separating the fixing portion 351 from the main body 352 and a fold separating the central portion 352a and the oblique side 352b of the main body 352 are provided.

  The main body 352 continuously connects the fixing portions 351 and transmits the displacement between the two fixing portions 351. In the example shown in FIG. 7B, the central portion 352 a of the main body 352 floats from the piezoelectric element 110 in accordance with the expansion and contraction of the piezoelectric element 110, and this part moves away from or near the piezoelectric element 110 to form a pair of thin plate main bodies. The distance between the central portions 352a that are at least a part of the portion 352 changes. This distance is transmitted to the displacement sensor 155. By attaching the pair of thin plates to the piezoelectric actuator body 105, the thin plates viewed from the side form an octagonal outline as shown in FIG. 7B. Such a configuration is a displacement magnifying mechanism, and the displacement of the piezoelectric element 110 can be magnified 5 to 10 times.

  The displacement sensor 155 connects the central portions 352a, which are at least a part of the pair of U-shaped thin plate main portions 352, to each other. In this case, the U-shape indicates that there is a plane parallel to the displacement direction to which the displacement sensor 155 is attached at the center position connecting the two fixing surfaces perpendicular to the displacement direction and the two fixing surfaces. Thereby, when the bending of the main body portion 352 of each thin plate is deformed, the displacement of the piezoelectric actuator 300 can be detected by changing the distance between the connecting portions of the displacement sensor 155 and the transmission body 350. Since the displacement is reduced when the main body 352 is curved, the rib processing is performed on the four oblique sides 352b, which are the main body 352, by bending both ends in the direction perpendicular to the displacement direction when the piezoelectric actuator main body is incorporated. Alternatively, a rib structure may be used, or a thin ceramic plate made of alumina, zirconia, or the like may be joined to the four oblique sides 352b to have a reinforcing part extending in a direction parallel to the displacement direction. Thereby, the rigidity of the surface of the main body 352 can be improved, and the responsiveness of the displacement sensor can be improved.

  Further, the above-described transmission body 350 has been described as a configuration using two thin plates. However, if the U-shaped thin plate portion is arranged to face each other with the piezoelectric actuator main body 105 interposed therebetween, the transmission body 350 may be used. 350 may be formed of one thin plate. For example, in the transmission body 350 shown in FIG. 8, the main body 352 is continuous from one end of the fixing portion 351, but another main body is formed to face the main body 352 from another end. Is also good.

  In addition, the ribs for bending both ends of the main bodies 152 and 252 of the transmission bodies 150 and 250 in the above-described first and second embodiments in the direction perpendicular to the displacement direction when assembled into the piezoelectric actuator main body. Then, a rib structure may be adopted, or a thin ceramic plate made of alumina, zirconia, or the like may be joined to the main body portions 152 and 252 to have a reinforcing portion extending in a direction parallel to the displacement direction. Thereby, the rigidity of the surfaces of the main bodies 152 and 252 can be improved, and the responsiveness of the displacement sensor can be improved.

  Further, the main body portions 152, 252, 352 of the transmission bodies 150, 250, 350 in the first embodiment, the second embodiment, and the third embodiment are punched to have a plurality of through holes. Is also good. This makes it possible to reduce the weight of the main bodies 152, 252, and 352, and it is also possible to improve the responsiveness of the displacement sensor.

100, 300 Piezoelectric actuator 105 Piezoelectric actuator main body 110 Piezoelectric element 113 Piezoelectric layer 114, 115 Internal electrode 116, 117 External electrode 121, 122, 157, 158 Lead wire 126, 127, 159 Terminal 130 Projection 140 Seat 150, 250, 350 Transmission Body 151, 251, 351 Fixed area 151 a Area (area where active area is projected in the displacement direction)
152, 252, 352 Main body 155 Displacement sensor 156 Displacement sensor main body 160 Cap 170 Feedback control device 180 Drive power supply 190 Displacement control system 352a Central portion 352b Oblique portion

Claims (11)

A piezoelectric actuator that is displaced by application of a voltage,
A piezoelectric actuator body formed by connecting a plurality of piezoelectric elements in series,
At least two fixing portions respectively fixed at positions between the piezoelectric elements separated from each other in the displacement direction of the piezoelectric actuator main body, and a continuous connection between the fixing portions and displacement between the two fixing portions. A transmission body having a main body for transmitting
A displacement sensor for detecting the transmitted displacement,
A seat for fixing one end of the piezoelectric actuator body,
A cap having a bottomed cylindrical shape, containing therein the piezoelectric actuator main body, the transmission body and the displacement sensor, and having an open end sealed in a seat;
The piezoelectric actuator, wherein the displacement sensor is attached to the transmission body. The transmission body is formed of a U-shaped thin plate,
2. The piezoelectric actuator according to claim 1, wherein both bent front ends of the U-shaped thin plate are fixed to the piezoelectric actuator body as the fixing portions. 3.   The length in the displacement direction of the main body, which is a central portion between the fixing portions of the thin plate, is longer than a linear distance in the displacement direction between the fixing portions fixed to the piezoelectric actuator main body, and The piezoelectric actuator according to claim 2, wherein the portion is arranged to be bent by a compressive force between the two fixing portions.   4. The piezoelectric actuator according to claim 1, wherein the main body is a flat plate having a shape that does not resonate with the displacement of the piezoelectric actuator main body. 5. A pair of the U-shaped thin plates are provided in parallel with respect to the displacement direction,
The piezoelectric actuator according to claim 2, wherein the displacement sensor connects at least a part of the main bodies of the pair of U-shaped thin plates.   The piezoelectric actuator according to claim 1, wherein the fixing portion is fixed to the piezoelectric actuator body within a range in which an active region of the piezoelectric element is projected in a displacement direction.   The piezoelectric actuator according to claim 1, wherein the main body has a reinforcing portion extending in a direction parallel to the displacement direction.   8. The piezoelectric actuator according to claim 1, wherein the fixing portion is fixed to both end faces of one of the plurality of piezoelectric elements. 9.   The fixing portion is fixed to both end surfaces of an element connecting body to which two or more piezoelectric elements of the plurality of piezoelectric elements are connected, and the main body portion includes two or more piezoelectric elements between the fixing portions. The piezoelectric actuator according to any one of claims 1 to 7, wherein the piezoelectric actuator is disposed across the element.   The piezoelectric actuator according to any one of claims 1 to 9, wherein one of the driving terminals of the piezoelectric actuator body and one of the detection terminals of the displacement sensor are common. The piezoelectric actuator according to any one of claims 1 to 10, wherein a difference between a thermal expansion coefficient of the transmission body and a thermal expansion coefficient of the piezoelectric element is 10 ^10-6 / C or less. .

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