JP7109314B2 - 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; A pair of fixing portions fixed to positions between the piezoelectric elements separated from each other in the displacement direction of the actuator main body, and a main body portion provided continuously from the fixing portion and provided along the surface of the piezoelectric actuator main body. A transmission body, a displacement sensor for detecting the displacement of the piezoelectric actuator main body transmitted from the pair of transmission bodies, a seat for fixing one end of the piezoelectric actuator main body, and a bottomed cylindrical shape, the a piezoelectric actuator main body, a cap housing the pair of transmission bodies and the displacement sensor and having an open end sealed to a seat, wherein the displacement sensor has both ends of the body parts of the pair of transmission bodies respectively. It is characterized by being attached to

Accordingly, since the displacement sensor is not attached directly to the surface parallel to the displacement direction of the piezoelectric element, 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 element while preventing dielectric breakdown due to cracks due to restraint of displacement, 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. In addition, since the displacement sensor is arranged straddling the body portions provided along the surface of the piezoelectric actuator body, the displacement sensor is extended when the piezoelectric actuator is extended. Displacement becomes in-phase strain, improving controllability.

(2) Further, in the piezoelectric actuator of the present invention, each of the pair of transmission bodies is formed of an L-shaped thin plate, and a bent end portion of the L-shaped thin plate serves as the fixing portion, and the piezoelectric actuator main body It is characterized by adhering to 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, making it possible to improve the durability of the displacement sensor.

(3) In the piezoelectric actuator of the present invention, the pair of transmission bodies are connected without restraining the deformation of the displacement sensor, and the connection body is formed so as to be deformable according to the displacement of the pair of transmission bodies. It is characterized by further comprising: As a result, the connecting portion serves as a guide that suppresses positional deviation between the body portions of the pair of transmission bodies, suppresses erroneous detection of the displacement sensor due to the deviation of the body portions of the transmission body, and detects the displacement sensor. It is possible to facilitate correspondence between the value and the actual displacement of the piezoelectric actuator.

(4) Further, in the piezoelectric actuator of the present invention, the connecting bodies are provided as a pair in parallel with respect to the displacement direction of the piezoelectric actuator body and symmetrical about a center line connecting the centers of the pair of transmission bodies. It is characterized by having As a result, positional deviation of the pair of transmission bodies can be further suppressed, and the displacement direction of the pair of transmission bodies can be maintained parallel to the displacement direction of the piezoelectric actuator main body.

(5) Further, in the piezoelectric actuator of the present invention, each of the connecting bodies has a curved portion bent in a direction parallel to the surface of the piezoelectric actuator main body, and the curved portion is perpendicular to the displacement direction. It is characterized in that it is provided at a position overlapping with a part of the displacement sensor in the direction. As a result, when the displacement sensor is attached to the transmission body, the connecting portion supports the displacement sensor, so that the displacement sensor can be prevented from bending during attachment. As a result, the displacement of the piezoelectric actuator body can be accurately detected. Furthermore, since the connecting body and the displacement sensor are not fixed by fixing or the like, the deformation of the connecting body is facilitated and the displacement of the piezoelectric actuator body is detected without hindering the deformation of the displacement sensor according to the displacement of the piezoelectric actuator body. can be made easier.

(6) Further, in the piezoelectric actuator of the present invention, each of the connecting bodies has a curved portion bent in a direction perpendicular to the surface of the piezoelectric actuator main body, and the connecting body does not overlap the displacement sensor. It is characterized by being provided in the position. As a result, the deformation of the displacement sensor is not hindered, and the deformation of the connecting body can be facilitated, making it easier to detect the displacement of the piezoelectric actuator main body.

(7) 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.

(8) 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 of the transmission body in a direction perpendicular 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. It can be formed by attaching

(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. As a result, a large displacement can be measured by a plurality of piezoelectric elements, and 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. 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, 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 between the fixed 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.

(11) 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 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 from increasing, and the configuration in which the displacement sensor is accommodated in the cap improves environmental resistance. can be done.

(12) 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. (a) to (c) are a perspective view, a front view and a side view of the transmission body of the first embodiment, respectively. 1 is a schematic diagram of a displacement control system; FIG. (a) and (b) are a front cross-sectional view and a side cross-sectional view, respectively, showing a piezoelectric actuator of a second embodiment. (a) to (c) are a perspective view, a front view and a side view of a transmission body of a second embodiment, respectively. (a) and (b) are a front cross-sectional view and a side cross-sectional view, respectively, showing a piezoelectric actuator of a third embodiment. (a) to (c) are a perspective view, a front view and a side view, respectively, of a transmission body according to a 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 (separate type)]
(Configuration of Piezoelectric Actuator)
1(a) and 1(b) 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 sectional and bottom views of the seat 140 and the terminals 126, 127, 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 pair of transmission bodies 150a and 150b, a displacement sensor 155, and a cap 160, and expands and contracts upon application of voltage. do. 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 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.

Inside the cap 160, in addition to the piezoelectric actuator main body 105, a pair of transmission bodies 150a and 150b and a displacement sensor 155 are also accommodated. 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 bodies 150a and 150b 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 faces 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)
4(a) to (c) are a perspective view, a front view and a side view of a pair of transmission bodies 150a and 150b, respectively. A pair of transmission bodies 150 a and 150 b transmit 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 pair of transmission bodies 150a and 150b, the piezoelectric element 110 is not restricted in displacement. 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, large-displacement type piezoelectric elements and piezoelectric elements used at high temperatures are likely to crack due to the piezoelectric element itself being constrained by a displacement sensor or the like. can be prevented and reliability can be improved.

Each of the pair of transmission bodies 150a and 150b includes fixed portions 151a and 151b and body portions 152a and 152b. The fixing portions 151a and 151b 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 portions 152 a and 152 b are formed continuously from the fixing portions 151 a and 151 b and provided along the surface of the piezoelectric actuator body 105 .

As shown in FIG. 4, each of the pair of transmission bodies 150a and 150b is formed of an L-shaped thin plate, and bent tip portions of the L-shaped thin plate are fixed to the piezoelectric actuator main body 105 as fixing portions 151a and 151b. preferably. In this case, the L-shape means that there is a fixed surface perpendicular to the displacement direction and a uniform surface bent from the fixed surface to which the displacement sensor 155 is attached. Sufficient fixation is possible by using such a tip portion. Further, in the body portions 152a and 152b, by bending the outer peripheral portions along the two sides extending from the fixing portions 151a and 151b, the bent outer peripheral portions serve as reinforcing portions that serve as beams to increase the strength of the body portion and resonate. It is also possible to improve the frequency.

The fixed portions 151a and 151b are preferably fixed to the piezoelectric actuator main body 105 within a range (regions 153a and 153b 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. The inactive region is a region within the piezoelectric element 110 excluding the active region.

The fixed portions 151a and 151b are preferably fixed to both end faces of the continuous piezoelectric element 110 . In this way, by straddling the pair of transmission bodies 150a and 150b across a plurality of piezoelectric elements, a signal reflecting the overall displacement state of the piezoelectric actuator main body 105 can be obtained. 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. Note that it is possible to adjust the length between the fixed portions 151a and 151b according to the amount of displacement required for detection. By fixing the fixing portions 151a and 151b to both end surfaces of one piezoelectric element 110, the length of the main body portion 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 order to accurately transmit the displacement of the piezoelectric actuator 100 to the displacement sensor 155, the pair of transmission bodies 150a and 150b are preferably made of a material having high rigidity and a thermal expansion close to that of the piezoelectric element 110. For example, metals such as stainless steel and invar, or members obtained by bonding these to ceramic thin plates such as alumina and zirconia are suitable. By selecting a material having a coefficient of thermal expansion close to that of the piezoelectric element 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, and has both ends attached to a pair of transmission bodies 150a and 150b, respectively, and detects displacement transmitted from a part of the piezoelectric actuator main body 105. As shown in FIG. In this way, since the displacement sensor 155 is attached to the piezoelectric actuator body 105 via the pair of transmission bodies 150a and 150b, stress concentration and displacement of the piezoelectric element are constrained due to direct adhesion to the piezoelectric element. Therefore, it is possible to maintain excellent durability even with piezoelectric actuators that exhibit a larger displacement than standard products, such as high-displacement and high-temperature types.

Both ends of the displacement sensor 155 are attached to main body portions 152a and 152b of a pair of transmission bodies 150a and 150b, respectively. Thereby, the displacement of the piezoelectric element 110 can be detected through the transmission bodies 150a and 150b without restraining the displacement. As a result, it is possible to reduce the positioning error using the piezoelectric actuator while preventing dielectric breakdown due to cracks due to restraint of the displacement of the piezoelectric element. In addition, since the displacement sensor is arranged across the body portions provided along the surface of the piezoelectric actuator body, the displacement sensor 155 is also extended when the piezoelectric actuator 100 is extended. Displacement of the displacement sensor 155 becomes in-phase strain, improving controllability.

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 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 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, a pair of transmission bodies 150a and 150b are prepared in advance, each of which has fixed portions 151a and 151b at both ends bent from the ends of main body portions 152a and 152b.

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, a pair of transmission bodies 150a and 150b are 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. 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 main body 105 sealed in the cap 160 of the piezoelectric actuator 100 is provided with a pair of transmission bodies 150a and 150b and the displacement sensor 155, and is sealed in the cap 160 together with the piezoelectric actuator main 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 manufactured. 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 (Extendable Type 1)]
Although the pair of transmission bodies 150a and 150b are provided separately in the first embodiment, they may be connected. 6A and 6B are a front cross-sectional view and a side cross-sectional view showing the piezoelectric actuator 200 to which a pair of transmission bodies 250a and 250b are connected, respectively. 7(a) to (c) are a perspective view, a front view and a side view of transmission bodies 250a and 250b, respectively.

As shown in FIGS. 6(a), (b), and FIGS. 7(a) to (c), the transmission bodies 250a and 250b are connected by curved connecting bodies 255 and 256, respectively. The transmission bodies 250a, 250b with the curved connecting bodies 255, 256 formed side by side can also be regarded as thin plates with telescoping sections. The curved connecting bodies 255 and 256 are preferably provided symmetrically about a center line connecting the centers of the pair of transmitting bodies 250a and 250b and parallel to the displacement direction of the piezoelectric actuator main body 105. FIG.

As a result, positional deviation of the pair of transmission bodies 250 a and 250 b can be suppressed, and the displacement direction of the pair of transmission bodies 250 a and 250 b can be maintained parallel to the displacement direction of the piezoelectric actuator main body 105 . That is, the flatness of the surfaces of the thin plate body portions 252a and 252b can be maintained. As a result, it also leads to improvement in assembly and measurement accuracy.

Each of the connecting bodies 255 and 256 has curved portions 255a and 256a bent in a direction parallel to the surface of the piezoelectric actuator main body 105 (within the same plane of the connecting body). It is preferably provided at a position overlapping part of the displacement sensor 155 in the vertical direction. As a result, when the displacement sensor 155 is attached to the transmission bodies 250a and 250b, the bending portions 255a and 256a of the connecting portions 255 and 256 support the displacement sensor 155, thereby preventing the displacement sensor 155 from bending during attachment. be able to. As a result, the displacement of the piezoelectric actuator main body 105 can be accurately detected. Furthermore, since the connecting bodies 255 and 256 and the displacement sensor 155 are not fixed by fixing or the like, the deformation of the connecting bodies 255 and 256 is facilitated without hindering the deformation of the displacement sensor 155 according to the displacement of the piezoelectric actuator main body 105. , the displacement of the piezoelectric actuator main body 105 can be easily detected. In this way, an expansion mechanism is formed in the same plane of the connecting bodies 255 and 256 by having a spring mechanism like the curved portions 255a and 256a. The thickness of the pair of transmitting bodies 250a and 250b may be formed thinner than the thickness of the connecting bodies 255 and 256. This makes it possible to reduce the weight of the transmission bodies 250a and 250b while maintaining the rigidity of the coupling bodies 255 and 256, and to improve the responsiveness of the displacement sensor.

[Third Embodiment (Extendable Type 2)]
In the second embodiment, the curved portions 255a and 256a of the connecting bodies 255 and 256 are bent in a direction parallel to the surface of the piezoelectric actuator body 105, but they may be bent in a direction perpendicular to the surface of the piezoelectric actuator body 105. . 8A and 8B are a front sectional view and a side sectional view showing the piezoelectric actuator 300 in which the curved portions 355a and 356a are bent in the direction perpendicular to the surface of the piezoelectric actuator main body 105 (thickness direction of the coupling body), respectively. It is a diagram. 9(a)-(c) are a perspective view, a front view and a side view of transmission bodies 350a and 350b, respectively.

In the examples shown in FIGS. 9A to 9C, the connecting bodies 355 and 356 are symmetrical about the center line connecting the centers of the pair of transmitting bodies 350a and 350b and parallel to the displacement direction of the piezoelectric actuator main body 105. are provided in pairs. As a result, positional deviation of the pair of transmission bodies 350 a and 350 b can be suppressed, and the displacement direction of the pair of transmission bodies 350 a and 350 b can be maintained parallel to the displacement direction of the piezoelectric actuator main body 105 . That is, the flatness of the surfaces of the thin plate body portions 352a and 352b can be maintained. As a result, it also leads to improvements in assembly and measurement accuracy.

Each of the connecting bodies 355 and 356 has curved portions 355 a and 356 a bent in a direction perpendicular to the surface of the piezoelectric actuator body 105 , and the connecting bodies 355 and 356 are provided at positions that do not overlap the displacement sensor 155 . may This facilitates deformation of the coupling bodies 355 and 356 without hindering deformation of the displacement sensor 155, and facilitates detection of displacement of the pair of transmission bodies 350a and 350b. In this way, an expansion mechanism is formed in the thickness direction of the connecting members 355 and 356 by having a spring mechanism like the curved portions 355a and 356a. The thickness of the pair of transmitting bodies 350a and 350b may be formed thinner than the thickness of the connecting bodies 355 and 356. This makes it possible to reduce the weight of the transmission bodies 350a and 350b while maintaining the rigidity of the coupling bodies 355 and 356, and to improve the responsiveness of the displacement sensor.

In the above embodiment, the transmitting bodies 250a, 250b (350a, 350b) and the connecting bodies 255, 256 (355, 356) are integrally formed. 255, 256 (355, 356) may be configured by separate members and formed by joining the respective members. In this case also, the same effect as described above can be obtained.

Furthermore, in the above embodiment, a mode using a pair of connecting bodies 255 and 256 (355 and 356) has been described, but one connecting body or a plurality of three or more connecting bodies may be used.

In addition, for the body portions 152a, 152b, 252a, 252b, 352a, and 352b of the transmission bodies 150a, 150b, 250a, 250b, 350a, and 350b in the above-described first, second, and third embodiments, A rib structure is formed by bending both ends in a direction perpendicular to the displacement direction when incorporated into the piezoelectric actuator main body, or ceramic thin plates such as alumina and zirconia are applied to the main body portions 152a, 152b, 252a, 252b, 352a, and 352b. A configuration may be adopted in which a reinforcement portion extending in a direction parallel to the displacement direction is provided by joining. As a result, it is possible to improve the rigidity of the surfaces of the main body portions 152a, 152b, 252a, 252b, 352a, and 352b and improve the responsiveness of the displacement sensor.

In addition, with respect to the body portions 152a, 152b, 252a, 252b, 352a, and 352b of the transmission bodies 150a, 150b, 250a, 250b, 350a, and 350b in the above-described first, second, and third embodiments, A form having a plurality of through-holes may be formed by punching. This makes it possible to reduce the weight of the body portions 152a, 152b, 252a, 252b, 352a, and 352b, and to improve the responsiveness of the displacement sensor.

100, 200, 300 piezoelectric actuator 105 piezoelectric actuator main body 110 piezoelectric element 113 piezoelectric layers 114, 115 internal electrodes 116, 117 external electrodes 121, 122, 157, 158 lead wires 126, 127, 159 terminals 130 projections 140 seats 150a, 150b, 250a, 250b, 350a, 350b transmission bodies 151a, 151b fixing portions 152a, 152b, 252a, 252b, 352a, 352b body portions 153a, 153b regions (ranges of active regions projected in the displacement direction)
155 displacement sensor 156 displacement sensor main body 160 cap 170 feedback control device 180 drive power supply 190 displacement control system 255, 256, 355, 356 connecting body 255a, 256a, 355a, 356a bending portion

Claims (12)

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;
a main body having a fixing portion fixed to a position between the piezoelectric elements separated from each other in the displacement direction of the piezoelectric actuator main body, the main body being continuous from the fixing portion and provided along the surface of the piezoelectric actuator main body; a pair of transmitters having
a displacement sensor that detects the displacement of the piezoelectric actuator body transmitted from the pair of transmission bodies;
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 pair of transmission bodies, and the displacement sensor therein, and having an open end sealed with a seat;
A piezoelectric actuator, wherein both ends of the displacement sensor are attached to respective body portions of the pair of transmission bodies. Each of the pair of transmission bodies is formed of an L-shaped thin plate,
2. The piezoelectric actuator according to claim 1, wherein a bent tip portion of said L-shaped thin plate is fixed to said piezoelectric actuator main body as said fixing portion. 2. A connection body that connects the pair of transmission bodies without constraining deformation of the displacement sensor and that is formed so as to be deformable according to displacement of the pair of transmission bodies. Item 3. The piezoelectric actuator according to item 2. 4. The piezoelectric actuator according to claim 3, wherein the connecting bodies are provided as a pair in parallel with respect to the displacement direction of the piezoelectric actuator main body and symmetrical with respect to a center line connecting the pair of transmitting bodies. Each of the connecting bodies has a curved portion bent in a direction parallel to the surface of the piezoelectric actuator main body, and the curved portion overlaps a part of the displacement sensor in a direction perpendicular to the displacement direction. 5. The piezoelectric actuator according to claim 4, further comprising: Each of the connecting bodies has a curved portion bent in a direction perpendicular to the surface of the piezoelectric actuator main body, and the connecting body is provided at a position not overlapping the displacement sensor. Item 5. The piezoelectric actuator according to item 4. 7. 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. 8. The piezoelectric actuator according to any one of claims 1 to 7, wherein the body portion has a reinforcing portion extending in a direction parallel to the displacement direction. 9. The fixing portion according to claim 1, wherein 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. piezoelectric actuator. 10. The piezoelectric actuator according to any one of claims 1 to 9, wherein the fixing portion is fixed to both end surfaces of one of the plurality of piezoelectric elements. 11. 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. 12. The piezoelectric actuator according to claim 1, 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. .

Images