JP7164864B2 - piezoelectric actuator - Google Patents

Description

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

A piezoelectric element that constitutes a piezoelectric actuator exhibits hysteresis in the process of expansion and contraction. Therefore, in precision positioning applications used in the manufacture of semiconductors and high-definition liquid crystals, feedback control is performed using displacement sensors to reduce positioning errors due to hysteresis. Piezoelectric actuators are also used in flow control valves for precisely supplying various gases to semiconductor manufacturing equipment, and fine movement mechanisms in precision numerically controlled processing machines. In addition, as the control of medical manipulators and the attitude control of aerospace vehicles become more sophisticated, the use of piezoelectric actuators that can be controlled with high precision is being studied.

Feedback control of piezoelectric actuators often employs an external sensor that detects displacement. When such a feedback control method is applied, highly accurate positioning becomes possible, but the system becomes complicated and expensive, and the application is limited. On the other hand, a simplified feedback control has been proposed in which a displacement sensor such as a strain gauge is directly attached to a resin-sealed piezoelectric actuator body and a partial displacement signal is used (see Patent Document 1).

JP-A-5-206536

However, although the piezoelectric actuator described in Patent Document 1 is simply sealed, strain gauges, which are relatively inexpensive displacement sensors, are used in harsh environments such as high humidity and corrosive gases. , the deterioration of its characteristics is inevitable, and it is difficult to use it stably for a long period of time. Further, when the displacement sensor is directly attached to the piezoelectric element, the displacement of the piezoelectric element is partially restrained, which causes cracks in the piezoelectric element and causes dielectric breakdown.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a piezoelectric actuator that can be used in harsh environments and that can accurately detect the displacement of a piezoelectric element without restricting the displacement. do.

(1) In order to achieve the above objects, the piezoelectric actuator of the present invention is a piezoelectric actuator that is displaced by application of a voltage, comprising: a piezoelectric actuator main body formed by connecting a plurality of piezoelectric elements in series; At least two fixing parts respectively fixed to positions between the piezoelectric elements separated from each other in the displacement direction of the actuator body and continuously connecting the fixing parts and transmitting displacement between the two fixing parts a displacement sensor for detecting the transmitted displacement; a seat for fixing one end of the piezoelectric actuator body; a cap that accommodates the transmission body and the displacement sensor and has an open end sealed to a seat, wherein the displacement sensor is attached to the transmission body.

As described above, since the displacement sensor is not attached directly to the surface of the piezoelectric element parallel to the displacement direction, the displacement of the piezoelectric element can be detected via the transmission body without restraining the displacement. As a result, it is possible to detect the amount of displacement of the piezoelectric actuator main body while preventing dielectric breakdown due to cracks due to displacement restraint, and to reduce positioning errors when performing positioning using the piezoelectric actuator. In addition, the cap can protect the piezoelectric actuator body and the displacement sensor from the surrounding environment, thereby improving the reliability and durability of the piezoelectric actuator.

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

(3) Further, in the piezoelectric actuator of the present invention, the length in the displacement direction of the body portion, which is the central portion between the fixed portions of the thin plate, is equal to the length between the fixed portions fixed to the piezoelectric actuator. It is longer than the linear distance in the displacement direction, and the body portion is bent by the compressive force between the two fixing portions. As a result, when the piezoelectric actuator body is displaced, the transmission body, which is arranged to be bent in advance, also moves in the direction in which the bending is canceled in accordance with the displacement of the piezoelectric actuator body, particularly in response to the extension of the piezoelectric actuator body. , the piezoelectric actuator body is not restrained by the transmission body. Therefore, it is possible to suppress the occurrence of cracks or the like in the piezoelectric element and stably transmit the displacement to the displacement sensor.

(4) Further, in the piezoelectric actuator of the present invention, the body portion is a flat plate having a shape that does not resonate with displacement of the piezoelectric actuator body. Thereby, responsiveness to displacement can be improved. The shape that does not resonate with displacement of the piezoelectric actuator main body means forming the main body 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, a pair of U-shaped thin plates are provided in parallel with respect to the displacement direction, and the displacement sensor is at least one of the main body portions of the pair of U-shaped thin plates. It is characterized in that the parts are connected to each other. Accordingly, when the main body portion of each thin plate is deformed, the displacement of the piezoelectric actuator can be detected by changing the distance at which the pair of thin plates are connected by the displacement sensor.

(6) Further, in the piezoelectric actuator of the present invention, the fixed portion is fixed to the piezoelectric actuator main body within a range obtained by projecting the active region of the piezoelectric element in the displacement direction. Thereby, the displacement can be detected without restricting the stress generated between the inactive region and the active region.

(7) Further, in the piezoelectric actuator of the present invention, the body portion 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 be, for example, a rib structure formed by bending the outer edge portion of the main body portion of the transmission body in a direction parallel to the displacement direction of the piezoelectric actuator main body, or a ceramic thin plate such as alumina or zirconia is attached to the main body portion. It can be formed by attaching

(8) Further, in the piezoelectric actuator of the present invention, the fixing portion is fixed to both end surfaces of one of the plurality of piezoelectric elements. This makes it possible to minimize the length of the body portion between the fixing portions and improve the responsiveness of the displacement sensor. 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 of the present invention, the fixing portion is fixed to both end surfaces of an element connecting body to which two or more piezoelectric elements among the plurality of piezoelectric elements are connected, and the body portion is arranged across two or more piezoelectric elements between the fixed portions. As a result, it is possible to measure a large variation due to a plurality of piezoelectric elements, improving the measurement accuracy. Also, a signal closer to the displacement of the entire piezoelectric actuator can be obtained than when measuring the displacement between one piezoelectric element. Furthermore, displacement amounts of a plurality of piezoelectric elements can be measured by displacement sensors, and the number of piezoelectric elements without displacement sensors can be reduced. Therefore, it is possible to reduce the positioning error caused by the change in the displacement amount of the piezoelectric element at the location where the displacement sensor is not arranged.

(10) Further, the piezoelectric actuator of the present invention is characterized in that one of the terminals for driving the piezoelectric actuator main body and one of the terminals for detection of the displacement sensor are common. As a result, when the displacement sensor is accommodated in the cap, the total number of terminals pulled out from the seat is suppressed from increasing, and the configuration in which the displacement sensor is accommodated in the cap improves environmental resistance. can be done.

(11) Further, in the piezoelectric actuator of the present invention, the difference between the thermal expansion coefficient of the transmitter and the thermal expansion coefficient of the piezoelectric element is 10×10 ⁻⁶ /° C. or less. As a result, deviation of the output of the displacement sensor due to temperature change can be suppressed.

According to the present invention, it can be used even in a severe environment, and the displacement of the piezoelectric element can be accurately detected without restricting the displacement.

1A and 1B are a front cross-sectional view and a side cross-sectional view, respectively, showing the piezoelectric actuator of the first embodiment; FIG. (a) and (b) are a front cross-sectional view and a bottom view of a seat and a terminal, respectively. It is a front sectional view of a piezoelectric element. 1 is a perspective view of a transmission body of the first embodiment; FIG. 1 is a schematic diagram of a displacement control system; FIG. FIG. 5 is a perspective view of a transmission body of a second embodiment; (a) and (b) are a front cross-sectional view and a side cross-sectional view, respectively, showing a piezoelectric actuator of a third embodiment. FIG. 11 is a perspective view of one of a pair of thin plates that constitute the transmission body of the third embodiment;

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 each drawing, and overlapping descriptions are omitted.

[First embodiment (curved type)]
(Configuration of Piezoelectric Actuator)
1A and 1B are a front cross-sectional view and a side cross-sectional view, respectively, showing the piezoelectric actuator 100. FIG. 2(a) and 2(b) are front cross-sectional and bottom views of seat 140 and terminals 126, 127 and 159, respectively. It should be noted that the piezoelectric actuator 100 shown in the reference diagram is merely 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, a sensor terminal 159, a seat 140, a transmission body 150, a displacement sensor 155, and a cap 160, and expands and contracts upon application of voltage. The piezoelectric actuator 100 is used, for example, in a valve opening/closing control section of a mass flow controller or a stage driving section of a precision positioning device, in which case it 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, the piezoelectric actuator main body 105 is displaced at the tip by the expansion and contraction of each piezoelectric element 110. FIG. Driving terminals 126 and 127 are connected to lead wires 121 and 122 of the piezoelectric actuator main body 105 and transmit applied voltage to the lead wires 121 and 122 .

The seat 140 is adhered to the end of the piezoelectric actuator body 105 and fixed at one end to support the piezoelectric actuator body 105 . The extension and contraction of the piezoelectric actuator body 105 to which the end on the side of the seat 140 is fixed displaces the protrusion 130 on the tip side.

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 hermetically sealing the piezoelectric actuator main body 105 and the displacement sensor 155, which are vulnerable to humidity and corrosive gases, with a low-humidity inert gas. For example, when used in a precision machine where the displacement device is wet with cutting water, or in a piezoelectric valve that controls the flow rate of corrosive gas, the positioning accuracy using a piezoelectric actuator is insufficient in open control, and the displacement sensor It is effective to perform positioning and the like by a piezoelectric actuator capable of performing feedback control by .

In this manner, the sealing allows the piezoelectric actuator 100 to operate without problems even in harsh environments such as high humidity and corrosive gas. Since the inside of the cap 160 has a completely airtight structure, it can be used in environments such as humidity and corrosive gases that impede the durability of the piezoelectric element and the displacement sensor, leading to expansion of applications.

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

One of the terminals 126 and 127 for driving the piezoelectric actuator main body 105 and one of the terminals for detection of the displacement sensor 155 are preferably shared. For example, a GND terminal can be shared. As a result, when the displacement sensor is accommodated in the cap, the total number of terminals pulled out from the seat is suppressed, and it is easy to adopt a configuration with improved environmental resistance in which the displacement sensor is accommodated in the cap. can. Separate terminals may be used instead of using a common terminal.

The cap 160 has a bottomed cylindrical shape with an open end and is made of metal. The cap 160 accommodates the piezoelectric actuator body 105 in close contact with it in the stacking direction, and its open end is joined to the seat 140 to seal the inside of the cap 160 . This protects the piezoelectric actuator 100 and improves durability.

The cap 160 has a diaphragm at the tip of the cap with a dome-shaped portion abutting the projection 130 . The straight tube portion of the cap 160 is formed cylindrical from the center to the bottom of the cap 160 . The diaphragm is formed in a dome shape. The cap 160 is desirably made of a material such as SUS316, SUS316L, or the like, which has excellent spring properties. A base secures the seat 140 , and the seat 140 supports the end of the piezoelectric actuator body 105 . Displacement is transmitted from the piezoelectric actuator 100 to the driven body by contacting the tip of the cap 160 with the driven body.

In addition to the piezoelectric actuator main body 105 , the transmission body 150 and the displacement sensor 155 are also housed inside the cap 160 . 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, the piezoelectric actuator 100 has a displacement sensor 155 arranged inside the cap 160 and a sensor terminal 159 provided on the seat 140 . As a result, in the piezoelectric actuator 100 incorporating the displacement sensor 155 , a displacement signal of the piezoelectric element 110 can be received via the sensor terminal 159 . Details of the transmission body 150 and the displacement sensor 155 will be described later.

(piezoelectric actuator body)
Piezoelectric actuator main body 105 is composed of piezoelectric element 110 , lead wires 121 and 122 and projection 130 . A plurality of piezoelectric elements 110 constituting the piezoelectric actuator main body 105 are arranged and connected in series (multi-connection), and their end surfaces are adhered to each other with an adhesive. A large amount of displacement can be ensured by bonding the plurality of piezoelectric elements 110 . Note that "in series" means the expansion/contraction direction, that is, the lamination direction of the piezoelectric layers and internal electrodes in the piezoelectric element 110 .

The lead wires 121 and 122 connect driving terminals 126 and 127 to the external electrodes 117 of the piezoelectric elements 110 . The connection is made in the same way on the side opposite to the side shown in FIG. 1(b).

The protrusion 130 is made of an inorganic material and has a hemispherical shape, and is provided on the tip side of the piezoelectric actuator main body 105 that transmits displacement to the driven body. The protrusion 130 and the piezoelectric actuator main body 105 are firmly adhered, and the protrusion 130 contacts the dome-shaped inner portion of the cap 160 .

(Piezoelectric element)
FIG. 3 is a front sectional view of the piezoelectric element 110. FIG. 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 laminated. Also, the external electrodes 116 and 117 are connected to the internal electrodes 114 and 115 on the side surfaces of the piezoelectric element 110 . The piezoelectric layer can be composed of a piezoelectric material such as PZT, barium titanate, or the like. Ag, Ag—Pd, Pt, or the like can be used as the electrode material.

(transmission body)
FIG. 4 is a perspective view of the transmission body 150 before incorporation. 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 constraint on the piezoelectric element 110 does not occur. Therefore, it is possible to prevent dielectric breakdown of the piezoelectric element due to displacement restraint when the displacement sensor is directly attached. In particular, a large displacement type piezoelectric element or a piezoelectric element used at high temperatures is likely to crack due to the piezoelectric element itself being constrained by a displacement sensor or the like. The piezoelectric actuator 100 can prevent such cracks and improve reliability.

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

As shown in FIG. 4, it is preferable that the transmission body 150 is formed of a U-shaped thin plate, and bent ends 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 means that there is a fixed surface perpendicular to the displacement direction and a uniform surface connecting between them and on which the displacement sensor 155 can be attached.

Sufficient fixation is possible by using such both ends. In addition, in the example shown in FIG. 4, the body portion 152 forms a central portion between the thin plate fixing portions 151 . The length of the body portion 152 in the displacement direction is longer than the linear distance in the displacement direction between the fixed portions 151 fixed to the piezoelectric actuator body 105 , and the body portion 152 is bent by the compressive force between the two fixed portions 151 . It is preferably arranged. For example, a main body portion longer than the length of the piezoelectric element by 0.2 to 2% is bent and incorporated, and the displacement sensor 155 is attached. As a result, when the piezoelectric actuator body is displaced, the transmission body, which is arranged to be bent in advance, also moves in the direction in which the bending is canceled in accordance with the displacement of the piezoelectric actuator body, particularly in response to the extension of the piezoelectric actuator body. , the piezoelectric actuator body is not restrained by the transmission body. Therefore, it is possible to suppress the occurrence of cracks or the like in the piezoelectric element and stably transmit the displacement to the displacement sensor 155 .

The fixed portion 151 is preferably fixed to the piezoelectric actuator main body 105 within a range (region 151a in the example of FIG. 4) obtained by projecting the active region of the nearest piezoelectric element 110 in the displacement direction. Thereby, 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 each other when viewed from the displacement direction. Also, the inactive region is a region within the piezoelectric element 110 excluding the active region.

The fixed portions 151 are fixed to both end faces of one piezoelectric element 110 . This makes it possible to minimize the length of the body portion between the fixing portions and improve the responsiveness of the displacement sensor. 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. Note that it is possible to adjust the length between the fixed portions 151 according to the amount of displacement required for detection. A signal reflecting the overall displacement state of the piezoelectric actuator main body 105 can be obtained by making the transmission body 150 extend over a plurality of piezoelectric elements. As a result, the displacement can be detected for a length close to the entire length of the piezoelectric actuator body 105 . In addition, displacement amounts of a plurality of piezoelectric elements can be measured by displacement sensors, and the number of piezoelectric elements without displacement sensors can be reduced. Therefore, it is possible to reduce the positioning error caused by the change in the displacement amount of the piezoelectric element at the location where the displacement sensor is not arranged.

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

By selecting a material having a coefficient of thermal expansion close to that of the piezoelectric element 110 for the transmission body 150, it is possible to suppress output errors caused by temperature changes. For example, the difference between the thermal expansion coefficient of the transfer body 150 and the thermal expansion coefficient of the piezoelectric element 110 is preferably 10×10 ⁻⁶ /° C. or less. As a result, it is possible to suppress the output deviation between the piezoelectric element 110 and the transmission body 150 due to the temperature change. If it is desired to measure the amount of displacement precisely, the thermal expansion of the transmission body 150 and the piezoelectric element 110 may be measured to correct the amount of displacement.

(displacement sensor)
The displacement sensor 155 is composed of, for example, a strain gauge, is attached to the transmission body 150 , and detects displacement transmitted from a portion of the piezoelectric actuator main 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 and displacement of the piezoelectric element due to direct adhesion to the piezoelectric element are not constrained. Good durability can be maintained even with piezoelectric actuators that exhibit greater displacement than standard products, such as displacement type and high temperature type.

The displacement sensor 155 is connected to a displacement sensor main body 156 and lead wires 157 and 158 , and the lead wire 158 is connected to a sensor terminal 159 to transmit the detected displacement. As a result, the displacement of the piezoelectric actuator main 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)
A displacement control system 190 can be configured using the piezoelectric actuator 100 described above. FIG. 5 is a schematic diagram of displacement control system 190 . As shown in FIG. 5, displacement control system 190 includes piezoelectric actuator 100 , feedback controller 170 and drive power supply 180 .

Sensor terminal 159 of displacement sensor 155 is connected to feedback controller 170 . A signal of the detected displacement is input to the feedback control device 170, and the feedback control device 170 converts the detected signal into the displacement of the piezoelectric actuator 100 and calculates the necessary driving amount based on the detected displacement. do. Conversion from the detection signal to displacement is in reverse 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 the 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 source 180 according to the calculated drive amount, and the drive power source 180 applies the voltage commanded by the feedback control device 170 to the piezoelectric actuator main body 105 . In this way, a displacement control system 190 with reduced errors can be realized.

(Manufacturing method of piezoelectric actuator)
Next, a method for 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 laminated is manufactured. Specifically, an electrode paste such as Ag or Ag—Pd is printed on green sheets of piezoelectric ceramics, laminated, pressure-bonded, and fired. Next, external electrodes 116 and 117 connected to the internal electrodes are formed along the stacking direction on the side surfaces of the piezoelectric element 110 . The external electrodes 116 and 117 can be formed by printing the electrode paste on the side surface of the piezoelectric element 110 and baking it. On the other hand, the transmitting body 150 is prepared in advance, in which the length of the body portion 152 is 1% longer than the length of the piezoelectric element 110, and both ends bent from the ends of the body portion 152 are fixed portions 151. FIG.

An adhesive such as epoxy is applied to the end surfaces of the plurality of piezoelectric elements 110 obtained in the stacking direction, and the elements are connected in series. At that time, the transmission body 150 is adhered 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 that time, only the projected area in the displacement direction of the active area of the piezoelectric element is bonded. In this way, multiple connections are made and the adhesive is cured. Then, a plate-shaped lead wire made of metal is fixed to the external electrode, so that the piezoelectric actuator main body 105 with multiple connections can be manufactured.

The above piezoelectric actuator main body 105 is placed on the seat 140, and a cap 160 is placed over it for sealing. At this time, the piezoelectric actuator body 105 sealed in the cap 160 of the piezoelectric actuator 100 is provided with the transmission body 150 and the displacement sensor 155 and sealed in the cap 160 together with the piezoelectric actuator body 105 . Lead wires 121 , 122 , 158 connected to terminals of displacement sensor 155 and drive electrodes are connected to terminals 126 , 127 , 159 inserted through seat 140 . Thus, the piezoelectric actuator 100 can be produced. The driving terminals 126 and 127 are electrically connected to the driving power source 180 and the sensor terminal 159 is electrically connected to the feedback control device 170 .

[Second embodiment (trapezoidal or irregular)]
In the above-described embodiment, the transmission body 150 is a rectangular thin plate bent into a U shape, but may be of another shape to prevent resonance. FIG. 6 is a perspective view of the transmission body 250. FIG. The transmission body 250 has two fixed portions 251 and a body portion 252 . The body portion 252 is preferably a flat plate having a shape that does not resonate with displacement of the piezoelectric actuator body 105 . In the example shown in FIG. 6, the body portion 252 is formed in a trapezoidal shape. As a result, resonance of the transmission body 250 against displacement of the piezoelectric actuator main body 105 can be prevented, and responsiveness to 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 transmitting body 150 is formed using one thin plate, but the transmitting body 350 may be configured using two thin plates. 7A and 7B are a front cross-sectional view and a side cross-sectional view, respectively, showing the piezoelectric actuator 300. FIG. FIG. 8 is a perspective view of one of a pair of thin plates that constitute the transmission body 350. FIG.

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

The body portion 352 continuously connects the fixing portions 351 and transmits displacement between the two fixing portions 351 . In the example shown in FIG. 7(b), the central portion 352a of the body portion 352 is floating from the piezoelectric element 110 according to the expansion and contraction of the piezoelectric element 110, and this portion moves away from or near to the main body of the pair of thin plates. The distance between the central portion 352a, which is at least part of the portion 352, varies. This distance is transmitted to displacement sensor 155 . By attaching a pair of thin plates to the piezoelectric actuator main body 105, the thin plates form an octagonal outline when viewed from the side as shown in FIG. 7(b). Such a configuration serves as a displacement magnifying mechanism, and can magnify the amount of displacement of the piezoelectric element 110 by 5 to 10 times.

The displacement sensor 155 connects central portions 352a, which are at least portions of a pair of U-shaped thin plate body portions 352, to each other. In this case, the U-shape means that there is a plane parallel to the displacement direction on which the displacement sensor 155 is attached at the central position connecting two fixed surfaces perpendicular to the displacement direction. As a result, the displacement of the piezoelectric actuator 300 can be detected by changing the distance between the displacement sensor 155 and the transmission body 350 when the body portion 352 of each thin plate is deformed. Since the displacement decreases when the main body portion 352 is bent, the four oblique side portions 352b of the main body portion 352 are rib-processed to bend both ends in the direction perpendicular to the displacement direction when incorporated into the piezoelectric actuator main body. Alternatively, a structure may be employed in which a ceramic thin plate such as alumina or zirconia is bonded to the four oblique side portions 352b to provide a reinforcing portion extending in the direction parallel to the displacement direction. Thereby, it is possible to improve the rigidity of the surface of the body portion 352 and improve the responsiveness of the displacement sensor.

In addition, although the transmission body 350 described above is configured to use two thin plates, the transmission body 350 may have a configuration in which U-shaped thin plate portions are arranged to face each other with the piezoelectric actuator main body 105 interposed therebetween. 350 may be formed from a single thin plate. For example, in the transmitting body 350 shown in FIG. 8, the main body portion 352 is continuous from one end of the fixing portion 351, and another main body portion is formed so as to face the main body portion 352 from another end. good too.

Further, the body portions 152, 252 of the transmission bodies 150, 250 in the above-described first and second embodiments are subjected to rib processing for bending both ends in the direction perpendicular to the displacement direction when incorporated into the piezoelectric actuator body. Alternatively, a rib structure may be provided, or a ceramic thin plate such as alumina or zirconia may be bonded to the main body portions 152 and 252 to provide a reinforcing portion extending in a direction parallel to the displacement direction. Thereby, it is possible to improve the rigidity of the surfaces of the body portions 152 and 252 and improve the responsiveness of the displacement sensor.

Further, a plurality of through holes are formed by punching the body portions 152, 252, and 352 of the transmission bodies 150, 250, and 350 in the first, second, and third embodiments described above. good too. This makes it possible to reduce the weight of the main body portions 152, 252, and 352 and improve the responsiveness of the displacement sensor.

100, 300 Piezoelectric actuator 105 Piezoelectric actuator body 110 Piezoelectric element 113 Piezoelectric layers 114, 115 Internal electrodes 116, 117 External electrodes 121, 122, 157, 158 Lead wires 126, 127, 159 Terminal 130 Projection 140 Seat 150, 250, 350 Transmission Body 151, 251, 351 Fixed portion 151a Region (range of active region projected in 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 Center part 352b Oblique side part

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 fixed portions respectively fixed to positions between the piezoelectric elements separated from each other in the displacement direction of the piezoelectric actuator body; a transmission body having a main body for transmitting the
a displacement sensor that detects the transmitted displacement;
a seat for fixing one end of the piezoelectric actuator body;
a cap formed in a cylindrical shape with a bottom, housing the piezoelectric actuator main body, the transmission body, and the displacement sensor therein, and having an open end sealed with a seat;
The main body portion is bent by a compressive force between the two fixing portions, and
A 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 end portions of said U-shaped thin plate are fixed to said piezoelectric actuator main body as said fixing portions. The length in the displacement direction of the main body portion, which is the central portion between the fixed portions of the thin plate, is longer than the linear distance in the displacement direction between the fixed portions fixed to the piezoelectric actuator main body. 3. A piezoelectric actuator according to claim 2. 4. The piezoelectric actuator according to any one of claims 1 to 3, wherein the body portion is a flat plate having a shape that does not resonate with displacement of the piezoelectric actuator body. A pair of U-shaped thin plates are provided in parallel with respect to the displacement direction,
3. The piezoelectric actuator according to claim 2, wherein the displacement sensor connects at least parts of the main body portions of the pair of U-shaped thin plates. 6. The piezoelectric actuator according to claim 1, wherein the fixed portion is fixed to the piezoelectric actuator main body within a range obtained by projecting the active region of the piezoelectric element in the displacement direction. 7. The piezoelectric actuator according to any one of claims 1 to 6, wherein the body portion 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 surfaces of one of the plurality of piezoelectric elements. The fixing portion is fixed to both end surfaces of an element connecting body to which two or more piezoelectric elements among the plurality of piezoelectric elements are connected, and the main body portion includes two or more piezoelectric elements between the fixing portions. 8. The piezoelectric actuator according to any one of claims 1 to 7, wherein the piezoelectric actuator is arranged across the elements. 10. The piezoelectric actuator according to claim 1, wherein one of the terminals for driving the piezoelectric actuator main body and one of the terminals for detection of the displacement sensor are shared. 11. The piezoelectric actuator according to any one of claims 1 to 10, wherein a difference between a thermal expansion coefficient of said transmitter and a thermal expansion coefficient of said piezoelectric element is 10×10 ⁻⁶ /° C. or less. .

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