JP6960348B2 - Piezoelectric actuator, self-propelled device, fluid transport device - Google Patents

Description

The present invention relates to a piezoelectric actuator, a self-propelled device using the piezoelectric actuator, and a fluid transport device.

Some actuators using piezoelectric elements (hereinafter, also referred to as piezoelectric actuators) utilize traveling waves. For example, in Patent Document 1 below, it is possible to generate a traveling wave that orbits the outer circumference in the plane of a rectangular flat plate-shaped piezoelectric element, and convert the tip portion of the piezoelectric element into an elliptical orbit that can be used for a feed operation. Describes the piezoelectric actuators that can be made. Further, as a device using a piezoelectric actuator capable of generating a traveling wave, there is a well-known ultrasonic motor.

Japanese Unexamined Patent Publication No. 2016-25708

The piezoelectric element used in the conventional piezoelectric actuator that generates a traveling wave is provided with a plurality of polarization regions having different polarization directions in one piezoelectric body. Therefore, the structure of the piezoelectric element becomes complicated, and the manufacturing cost of the piezoelectric actuator increases. Further, since it is necessary to provide a plurality of polarization regions in one piezoelectric body, if the piezoelectric actuator is to be miniaturized, the area of each polarization region becomes small, and it becomes difficult to obtain a large amplitude.

Therefore, an object of the present invention is to provide a piezoelectric actuator capable of generating a traveling wave with a large amplitude even with a simple structure, and a self-propelled device and a fluid transport device using the piezoelectric actuator.

One aspect of the present invention for achieving the above object is to use a first piezoelectric element on one main surface of a rectangular planar vibrating plate in which the extension direction of the long side is the front-rear direction and the extension direction of the short side is the left-right direction. The second piezoelectric element is attached,
The first piezoelectric element and the second piezoelectric element are formed by arranging electrode plates on both the front and back surfaces of a rectangular flat plate-shaped piezoelectric body.
The first piezoelectric element and the second piezoelectric element are arranged so as to be separated from each other in the front-rear direction of the diaphragm.
The diaphragm vibrates in the first vibration mode at the first resonance frequency and vibrates in the second vibration mode at the second resonance frequency.
In the first vibration mode, standing waves of two wavelengths are generated in the front-rear direction on the diaphragm with both front and rear ends as free ends.
In the second vibration mode, a standing wave for 1.5 wavelengths is generated in the front-rear direction with both front and rear ends as free ends, and at the position of the antinode of the standing wave for 1.5 wavelengths, the vibration plate With the left and right ends of the free end, standing waves of 1/2 wavelength are generated in the left and right direction.
The excitation region in the first vibration mode is a region between two adjacent nodes in the front-rear direction.
The first piezoelectric element is arranged at the center of the left and right in the excitation region on one of the front and rear of the first vibration mode.
The excitation region in the second vibration mode is an overlapping region between the region to the left or right with respect to the center of the left and right and the region between the nodes adjacent to each other in the front-rear direction in the standing wave in the front-rear direction.
The second piezoelectric element is arranged along the left end or the right end of the diaphragm and in the excitation region of the other front and rear in the second vibration mode, and the width in the left-right direction is the left-right width of the diaphragm. Is less than 1/2 of
It is a piezoelectric actuator characterized by this.

In the piezoelectric actuator, the left-right width of the first piezoelectric element may be ½ or more of the left-right width of the diaphragm.

Another aspect of the present invention is a self-propelled device configured by using the two piezoelectric actuators, wherein the self-propelled device is a self-propelled device.
The two piezoelectric actuators are connected in a state of being arranged in parallel on the left and right sides with the one main surface side of the diaphragm as the upper surface.
Propulsion portions are formed in a region along the left end of the lower surface of the diaphragm in the piezoelectric actuator on the left side and a region along the right end of the lower surface of the diaphragm in the piezoelectric actuator on the right side.
A driving signal having a phase difference of 90 ° is applied to the first piezoelectric element and the second piezoelectric element to generate a traveling wave in the plane of the diaphragm.
The propulsion unit transmits the traveling wave to the mounting surface by frictional force.
It is characterized by that.

The scope of the present invention also includes a fluid transport device configured by using the two piezoelectric actuators.
The two piezoelectric actuators are laminated in the vertical direction.
The upper piezoelectric actuator has the one main surface as the upper surface.
The lower piezoelectric actuator has the one main surface as the lower surface.
Between the upper and lower layers of the piezoelectric actuator, a partition wall extending from the front end to the rear end is formed in a region in the center of the left and right and a region along at least one of the left and right edges.
A fluid transport path that opens at both front and rear ends is formed between the layers by the partition wall.
A drive signal having a phase difference of 90 ° is applied to the first piezoelectric element and the second piezoelectric element to generate a traveling wave that orbits in the same direction on the diaphragm of the piezoelectric actuator above and below.
It is characterized by that.

According to the present invention, there is provided a piezoelectric actuator having a simple structure and capable of generating a traveling wave having a large amplitude. Further, by using the piezoelectric actuator, a self-propelled device and a fluid transport device having a simple structure are provided. Other effects will be clarified in the following description.

It is a figure which shows the piezoelectric actuator which concerns on embodiment of this invention. It is a figure which shows the connection state of the piezoelectric actuator and the drive circuit which concerns on the said Example. It is a figure which shows the resonance state (the first vibration mode) of the diaphragm which constitutes the piezoelectric actuator which concerns on the said Example. It is a figure which shows the resonance state (the second vibration mode) of the diaphragm which constitutes the piezoelectric actuator which concerns on the said Example. It is a figure which shows the arrangement of the piezoelectric element which comprises the piezoelectric actuator which concerns on the said Example. It is a figure which shows the state when the traveling wave is generated in the piezoelectric actuator which concerns on the said Example. It is a figure which shows the state when the standing wave is generated in the piezoelectric actuator which concerns on the said Example. It is a figure which shows the structure of the motor which used the piezoelectric actuator which concerns on the said Example. It is a figure which shows the structure of the self-propelled apparatus which used the piezoelectric actuator which concerns on the said Example. It is a figure which shows the structure of the fluid transport device which used the piezoelectric actuator which concerns on the said Example. It is a figure which shows other example of the said fluid transport device.

Examples of the present invention will be described below with reference to the accompanying drawings. In the drawings used in the following description, the same or similar parts may be designated by the same reference numerals and duplicate description may be omitted. Depending on the drawing, unnecessary reference numerals may be omitted in the description.

=== Piezoelectric actuator structure ===
FIG. 1 is a diagram showing a structure of a piezoelectric actuator 1 according to an embodiment of the present invention. Two piezoelectric elements (3a, 3b) are attached to one main surface 21 of a rectangular flat diaphragm 2 made of stainless steel or the like so as to be separated from each other in the front-rear direction. In the illustrated diaphragm 2, the ratio L: W of the length L and the width W is 5: 2. The two piezoelectric elements (3a, 3b) have a structure in which electrode plates are arranged on both the front and back surfaces of a flat plate-shaped piezoelectric body having a rectangular planar shape. Here, each of the upper and lower directions is defined with the one main surface 21 as the upper surface, the length L direction is the front-rear direction, and the width W direction is the left-right direction. Then, as shown in FIG. 1, when each of the front-rear directions and the left-right directions is defined, the front piezoelectric element (hereinafter, also referred to as the first piezoelectric element) has a rectangular flat plate shape having a front-rear length L1 and a width W1. Yes, it is arranged at the center of the left and right at the position of the distance D1 from the front end 22 to the rear end 23 of the diaphragm 2. The rear piezoelectric element (hereinafter, also referred to as the second piezoelectric element 3b) has a rectangular flat plate shape having a front-rear length L2 and a width W2, and is left at a position of a distance D2 from the front end 22 to the rear end 23 of the diaphragm 2. It is arranged along the edge edge (hereinafter, also referred to as the left edge 24). The second piezoelectric element 3b may be arranged along the right edge (hereinafter, also referred to as the right edge 25).

The two piezoelectric elements (3a, 3b) have a signal electrode to which a drive signal is applied formed on the upper surface of a rectangular flat plate-shaped piezoelectric body, and a ground electrode formed on the lower surface thereof. The signal electrode is, for example, a baked silver paste or the like. Further, in the exemplified piezoelectric actuator 1, the lower surface of the piezoelectric body is attached to a diaphragm 2 made of a conductor, and the diaphragm 2 also serves as a ground electrode. That is, in the piezoelectric elements (3a, 3b), a drive signal is applied to the signal electrode on the upper surface of the piezoelectric element (3a, 3b) with the diaphragm 2 as a common ground electrode. Then, in this embodiment, the two piezoelectric elements (3a, 3b) expand and contract in the front-rear direction with respect to the electric field in the up-down direction, with the up-down direction as the polarization direction.

FIG. 2 shows a diagram when the drive circuit 30 is connected to the piezoelectric actuator 1. FIG. 2 shows a state in which the piezoelectric actuator 1 is viewed from the right side. In the first piezoelectric element 3a and the second piezoelectric element 3b, a signal electrode 32 is formed on the upper surface of the piezoelectric body 31, and the lower surface of the piezoelectric body 31 is attached to the diaphragm 2 by, for example, a conductive adhesive. .. The ground side of the drive circuit 30 is connected to the diaphragm 2 so that signals can be individually applied to the signal electrodes 32 of the first piezoelectric element 3a and the second piezoelectric element 3b.

=== Vibration mode of diaphragm ===
The diaphragm 2 vibrates in a vibration mode peculiar to each of two different resonance frequencies. That is, one of the two resonance frequencies and the other vibrate in different vibration modes. In the piezoelectric actuator 1 according to the embodiment shown in FIG. 1, one of the two vibration modes (hereinafter, also referred to as the first vibration mode) is expressed on the vibration plate 2 by the first piezoelectric element 3a, and the second vibration mode is expressed. The other vibration mode (hereinafter, also referred to as a second vibration mode) is expressed by the piezoelectric element 3b.

As is well known, the natural resonance frequency of a structure is the natural frequency, and the natural frequency varies depending on the shape, Young's modulus of the material, and density. That is, the structures having the same shape differ only in the resonance frequency according to the physical properties of the material, and when vibrated at the resonance frequency, the vibration state becomes the same. Then, the vibration state of the structure can be faithfully reproduced by the simulation using the finite element method. 3 and 4 show the analysis results by the simulation. Specifically, the results of modal analysis (eigenvalue analysis) for investigating the natural frequency and the vibration shape at that frequency are shown.

FIG. 3 shows the vibration state of the vibrating plate 2 in the first vibration mode at the resonance frequency of 132.3 kHz, and FIG. 3 (A) is a perspective view showing the vibration state of the vibrating plate 2 in the resonance state. Yes, FIG. 3B is a diagram showing a waveform when the vibrating plate 2 in a resonant state is viewed from the right. As shown in FIG. 3A, the diaphragm 2 vibrates in a wavy manner in the front-rear direction at a resonance frequency of 132.3 kHz. Specifically, as shown in FIG. 3B, standing waves of two wavelengths are generated with the front end 22 and the rear end 23 as free ends. Therefore, in the diaphragm 2, the region 41 shown by the ellipse in FIG. 3 (A) and the region 41 in the front-rear direction shown by the double-headed arrow in FIG. The region 41 for half a wavelength between () is a region that can be excited (hereinafter, also referred to as an excitation region 41). Then, if the piezoelectric element is attached to the excitation region 41, the diaphragm 2 can be resonated in the vibration state shown in FIG. 3 (hereinafter, also referred to as the first vibration mode). Further, the front-rear length L1 of the piezoelectric element 3a in FIG. 1 needs to be equal to or less than the front-rear length of the excitation region 41. Further, in the excitation region 41, it is desirable that the front-rear center position of the first piezoelectric element 3a is at or near the position of the antinode P2a.

FIG. 4 shows the vibration state of the diaphragm 2 in the second vibration mode at the resonance frequency of 134.3 kHz. FIG. 4A is a perspective view showing the vibration mode of the diaphragm 2 in the resonance state at 134.3 kHz, and FIG. 4B is a perspective view of the diaphragm 2 in the resonance state when viewed from the right. It is a figure which shows the waveform. 4 (C) and 4 (D) are views of the deformed state of the diaphragm 2 at a certain moment when viewed from the front.

As shown in FIG. 4A, in the second vibration mode, the diaphragm 2 vibrates at a resonance frequency of 134.3 kHz so as to undulate in the front-rear direction and reverse each other in the left-right direction. Specifically, as shown in FIG. 4B, a standing wave of 1.5 wavelengths is generated on the diaphragm 2 with the front end 22 and the rear end 23 as free ends. Then, at the antinode position P2b in the standing wave in the anteroposterior direction, as shown in FIGS. 4 (C) and 4 (D), the node P3 is provided in the center of the left and right, and the left end 24 and the right end 25 are free ends. A standing wave for half a wavelength is generated. Therefore, in the diaphragm 2, the region 42 shown by the ellipse in FIG. 4A is the excitation region 42. Specifically, the excitation region 42 includes a region 42a for half wavelengths in the front-rear direction indicated by double-headed arrows in FIG. 3 (B) and a horizontal direction indicated by double-headed arrows in FIGS. 3 (C) and 3 (D). This is a region that overlaps with the region 42b for 1/4 wavelength of the above. Then, if the second piezoelectric element 3b is attached to any of the excitation regions 42, the diaphragm 2 can be resonated in the second vibration mode shown in FIG. Further, the front-rear length L2 of the second piezoelectric element 3b in FIG. 1 needs to be equal to or less than the front-rear length of the excitation region 42. Further, in the excitation region 42, it is desirable that the front-rear center position of the piezoelectric element is at or near the position of the antinode P2b.

=== Arrangement of piezoelectric elements ===
As described above, the diaphragm 2 resonates in the first vibration mode and the second vibration mode, which are different from each other, at the two resonance frequencies of 132.3 kHz and 134.3 kHz. Then, the first piezoelectric element 3a and the second piezoelectric element 3b are arranged in the excitation region 41 in the first vibration mode and the excitation region 42 in the second vibration mode, respectively, and these piezoelectric elements (3a, 3b) are arranged. Is driven at a frequency slightly deviated from the two resonance frequencies, a vibration in which the two vibration modes of the first vibration mode and the second vibration mode are combined is generated in the plane of the vibration plate 2. FIG. 5 shows the vibration state of the diaphragm 2 in the first vibration mode and the vibration state of the diaphragm 2 in the second vibration mode in an overlapping manner. In FIG. 5, the vibration waveform in the first vibration mode and the positions of the nodes P1a and the antinode P2a in the standing wave are shown by solid lines, and the vibration waveform in the second vibration mode and the positions of the nodes P1b and the antinode P2b in the standing wave are shown by chain lines. The arrangement of the first piezoelectric element 3a and the second piezoelectric element 3b will be described below with reference to FIG. 5 and FIGS. 1, 3, and 4 shown above.

In the piezoelectric actuator 1 according to the embodiment of the present invention shown in FIG. 1, the first piezoelectric element 3a is arranged within the range of the excitation region 41 in the first vibration mode shown in FIG. Further, by aligning the center of the plane region of the first piezoelectric element 3a with the position of the antinode P1b having the largest amplitude, a larger amplitude can be obtained.

Further, the second piezoelectric element 3b is arranged within the range of the excitation region 42 in the second vibration mode shown in FIG. Further, by aligning the center of the plane region of the second piezoelectric element 3b with the position of the antinode P2b having the largest amplitude, a larger amplitude can be obtained. However, in the second vibration mode, the antinode P2b is formed at the left end 24 or the right end 25 of the diaphragm 2. Therefore, when the position of the antinode P2b and the center of the plane region of the second piezoelectric element 3b are matched, the second vibration mode is performed. The piezoelectric element 3b protrudes from the left or right side of the diaphragm 2. Therefore, the second piezoelectric element 3b is arranged along the left end 24 or the right end 25 of the diaphragm 2.

The first piezoelectric element 3a and the second piezoelectric element 3b have an excitation region (41 or 42) in which one piezoelectric element (3a or 3b) is arranged so that their vibrations do not cancel each other out, and the other. It is necessary to prevent the piezoelectric element (3b or 3a) from overlapping with the excitation region (42 or 41) in which the piezoelectric element (3b or 3a) is arranged. Therefore, in the piezoelectric actuator 1 according to the embodiment shown in FIG. 1, as shown in FIG. 5, when the diaphragm 2 is viewed from the right, the center of the plane region of the first piezoelectric element 3a is the first. It is arranged in the vicinity of the antinode P10 in the foremost excitation region 41 in the vibration mode. Specifically, the first piezoelectric element 3a is arranged at the center of the left and right at the position where D1 = L / 4. Since the excitation region 41 in the first vibration mode is formed so as to cross the diaphragm 2 in the left-right direction, it is desirable that the left-right width W1 of the first piezoelectric element 3a is W / 2 or more.

Regarding the second piezoelectric element 3b, the left end 24 of the second piezoelectric element 3b is set so that the front-rear center position is close to the position of the antinode P20 of the rearmost excitation region 42 in the second vibration mode in the plane region. , Or the right end 25 is arranged along the left end 24 or the right end 25 of the diaphragm 2. Specifically, it is arranged along the left end 24 at the position where D2 = 0.7L (≈2L / 3). Since the excitation region 42 in the second vibration mode is a region from the left end 24 or the right end 25 of the diaphragm 2 to the center of the left and right, the left and right width W2 of the second piezoelectric element 3b needs to be W / 2 or less. There is.

=== Operation of piezoelectric actuator ===
In the piezoelectric actuator 1 of this embodiment, the first piezoelectric element 3a and the second piezoelectric element 3b are driven at a frequency of 130 kHz, and the phase difference of the drive signals applied to the two piezoelectric elements (3a, 3b) is 90 °. At some point, a traveling wave is generated in the plane of the vibrating plate 2. Further, when the phase difference of the drive signal is 0 ° or 180 °, a standing wave is generated. 6 and 7 show the transition of the deformed state of the diaphragm 2 when the piezoelectric actuator 1 is operated. FIG. 6 shows a state when a traveling wave is generated in the plane of the diaphragm 2. Here, the phase of the drive signal applied to the second piezoelectric element 3b is advanced by 90 ° with respect to the phase of the drive signal applied to the first piezoelectric element 3a. In the following, when the phase of the drive signal applied to the second piezoelectric element 3b is ahead of the phase of the drive signal applied to the first piezoelectric element 3a, the sign of the phase difference angle is “+”. If the phase is delayed, it is set to "-". That is, in FIG. 6, the phase difference of the drive signal is + 90 °.

As shown in FIG. 6, when a drive signal having a phase difference of + 90 ° is applied to the first piezoelectric element 3a and the second piezoelectric element 3b, the position of the mountain indicated by the black circle in the figure is accompanied by the generation of the traveling wave. Moves in the order of FIG. 6 (A), FIG. 6 (B), FIG. 6 (C), and FIG. 6 (D). That is, as shown by the thick arrow in the figure, the diaphragm 2 generates a traveling wave clockwise when viewed from above. If the phase difference is set to −90 °, a traveling wave counterclockwise is generated on the diaphragm 2 when viewed from above.

On the other hand, when the first piezoelectric element 3a and the second piezoelectric element 3b are driven in the same phase (phase difference 0 °), as shown in FIG. 7, at the positions indicated by white circles in the figure, like a standing wave node. There is almost no vibration, and the amplitude in the vertical direction becomes extremely small. At the position indicated by the black circle in the figure, it vibrates with a large amplitude in the vertical direction like the antinode of a standing wave. When the phase difference between the first piezoelectric element 3a and the second piezoelectric element 3b is set to 180 °, the position of the black circle in the figure becomes a node, and the position of the white circle in the figure becomes an antinode.

As described above, in the piezoelectric actuator 1 of the present embodiment, the first piece is formed on the upper surface 21 of the rectangular flat plate-shaped vibrating plate 2 in which the length L and the width W have a predetermined ratio (for example, L: W = 5: 2). It has a simple structure in which two piezoelectric elements, a piezoelectric element 3a and a second piezoelectric element 3b, are attached. Further, the two piezoelectric elements (3a, 3b) have a single polarization region, and it is not necessary to provide a plurality of regions having different polarization directions in one piezoelectric body 31. Further, the first piezoelectric element 3a and the second piezoelectric element 3b are attached to the excitation region 41 in the first vibration mode and the excitation region 42 in the second vibration mode of the vibrating plate 2, respectively, and these piezoelectric elements (3a, When 3b) is vibrated at a predetermined frequency (for example, 130 kHz), it is configured to generate a vibration that is a combination of vibrations in the two vibration modes of the first vibration mode and the second vibration mode described above. ing. Then, by setting the phase difference between the drive signals applied to the first piezoelectric element 3a and the second piezoelectric element 3b to 90 °, it is possible to generate a traveling wave that orbits in the plane on the diaphragm 2.

The piezoelectric actuator according to the present embodiment shown in FIG. 1 is used by using a diaphragm 2 made of a stainless steel plate having a predetermined thickness (for example, 1 mm) having a plane region having a length L = 5 cm and a width = 2 cm. When 1 was actually manufactured, it was confirmed that a vibration state similar to that in the simulation could be obtained with an amplitude of about 1 μm.

=== Application example ===
The piezoelectric actuator 1 according to the embodiment of the present invention can be applied to various devices. 8 to 11 show various devices using the piezoelectric actuator 1 according to the embodiment, respectively.

<Motor>
A motor is shown as a first application example of the piezoelectric actuator 1. FIG. 8 is a diagram showing the motor 10. The motor 10, which is the first application example, uses one piezoelectric actuator (hereinafter, also referred to as a basic unit 1) according to the embodiment of the present invention shown in FIG. At the right rear corner of the diaphragm 2 of the basic unit 1, a protrusion 11 made of an elastic body is formed so as to project rearward. Further, a disk-shaped rotor 13 which is pivotally supported by the rotating shaft 12 and has a surface parallel to the plate surface of the diaphragm 2 is provided. The tip of the protrusion 4 is in contact with the circumference of the rotor 6.

When a drive signal having a phase difference of + 90 ° is applied to the first piezoelectric element 3a and the second piezoelectric element 3b, the motor 10 shown in FIG. 8 is applied to the vibrating plate 2 from above as shown by the thick arrow in the figure. As you can see, a clockwise traveling wave is generated, and as shown by the white arrow in the figure, a traveling wave from the left to the right is generated at the tip of the protrusion 11. As a result, the rotor 13 rotates counterclockwise. When the phase difference between the drive signals applied to the first piezoelectric element 3a and the second piezoelectric element 3b is set to −90 °, the rotor 13 rotates clockwise.

<Self-propelled device>
Although the basic unit 1 can generate a traveling wave in the plane of the diaphragm 2, it is difficult to use the traveling wave as a propulsion force. Therefore, as a second application example, a self-propelled device capable of extracting propulsive force by using two basic units 1 will be mentioned. FIG. 9 shows a self-propelled device 110 which is a second application example. The self-propelled device 110 has a structure in which two basic units (1L, 1R) are connected in the left-right direction via a flat plate-shaped member 6, and the left basic unit 1L is connected to the left end side of the lower surface. Comb-shaped propulsion portions (7L, 7R) are provided on the right end side of the lower surface of the basic unit 1R on the right side. The propulsion unit (7L, 7R) generates a frictional force with respect to the mounting surface by bringing the tip end side of the comb teeth into contact with the mounting surface. On the lower surface of the diaphragm 2 of the left and right basic units (1L, 1R), the area where the propulsion unit (7L, 7R) is not provided does not contact the mounting surface and has a frictional force with respect to the mounting surface. Does not occur. As a result, when the left and right basic units (1L, 1R) generate traveling waves in opposite directions when viewed from above, propulsive force is generated forward or backward. In the example shown in FIG. 9, as shown by the thick arrow in the figure, a traveling wave counterclockwise is generated in the left basic unit 1L and clockwise in the right basic unit 1R when viewed from above. Is generating a traveling wave of. As a result, a traveling wave is generated at the tip of the comb tooth in the propulsion section (7L, 7R) from the rear to the front relative to the mounting surface. That is, the self-propelled device 110 self-propells backward. As for the state in which the drive signal is applied to each of the piezoelectric elements (3aL, 3bL, 3aR, 3bR) at this time, the phase difference between the first piezoelectric element 3aL and the second piezoelectric element 3bL is − for the left basic unit 1L. It is 90 °, and for the right basic unit 1R, the phase difference between the first piezoelectric element 3aR and the second piezoelectric element 3bR is + 90 °. That is, the first piezoelectric element 3aL of the left basic unit 1L and the second piezoelectric element 3bR of the right basic unit 1R are the first set, and the second piezoelectric element 3bL of the left basic unit 1L and the right one. Assuming that the first piezoelectric element 3aR of the basic unit 1R is the second set, the piezoelectric elements (3aL-3bR, 3bL-3aR) belonging to the same set are driven in the same phase, and the first set of piezoelectric elements (3aL, 3bR). When the phase of the second set of piezoelectric elements (3bL, 3aR) is advanced by 90 ° with respect to the phase of, the self-propelled device 110 self-propells backward. Then, when the phase of the second set of piezoelectric elements (3bL, 3aR) is delayed by 90 ° with respect to the phase of the first set of piezoelectric elements (3aL, 3bR), the self-propelled device 110 self-propells forward.

Further, the first piezoelectric element (3aL, 3aR) of the left and right basic units (1L, 1R) is driven in phase, and the second piezoelectric element (1L, 1R) of the left and right basic units (1L, 1R) is driven. When the phase of 3bL, 3bR) is advanced by 90 ° with respect to the first piezoelectric element (3aL, 3aR), the diaphragm 2 of the two basic units (1L, 1R) has a clockwise traveling wave when viewed from above. Occurs. As a result, the self-propelled device 110 turns counterclockwise on the spot when viewed from above. The first piezoelectric element (3aL, 3aR) of the left and right basic units (1L, 1R) is driven in phase, and the second piezoelectric element (3bL,) of the left and right basic units (1L, 1R) is driven. If the 3bR) is delayed by 90 ° with respect to the first piezoelectric element (3aL, 3aR), the self-propelled device 110 turns clockwise on the spot when viewed from above.

As described above, the self-propelled device 110, which is the second application example, has two piezoelectric elements (3aL, 3bL) in the left basic unit 1L and two piezoelectric elements (3aR, 3bR) in the right basic unit 1R. By making it possible to appropriately switch the phase of the drive signal applied to each of), it is possible to move forward, backward, and turn in the same manner as a vehicle having an endless track. The self-propelled device 110 shown here includes, for example, a parts transfer device at a production site, a toy, and the like. Of course, the use of the self-propelled device 110 shown here is not limited to these.

<Fluid transport device>
A third application example is a fluid transport device such as a pump. FIG. 10 is a diagram showing an example of the fluid transport device 210. As shown in FIG. 10, the fluid transport device 210 has a structure in which two basic units (1U, 1D) are vertically laminated. The lower basic unit 1D has its upper and lower surfaces inverted with respect to the upper basic unit 1U, and two piezoelectric elements (not shown) are attached to the lower surface of the diaphragm 2.

The fluid transport device 210 shown in FIG. 10 has a configuration for transporting a fluid in one direction in the front-rear direction, and is located at the left-right center and the right end between the layers of the two basic units (1U, 1D) from the front end to the rear end. A partition wall (8C, 8R) is formed. As a result, the two basic units (1U, 1D) face each other with a slight gap, and the two basic units (1U, 1D) are formed by the partition walls (8C, 8R) formed at the center of the left and right and the right end. A fluid transport path 9R that connects the front and back is formed on the right end side between the layers. Then, when a traveling wave that is vertically symmetrical, that is, a traveling wave that orbits in the same direction when viewed from above is generated in each of the upper basic unit 1U and the lower basic unit 1D, one of the front and rear of the fluid transport path 9R is generated. The fluid supplied to the openings is transported towards the other front and rear openings.

In the example shown in FIG. 10, as shown by the thick arrow in the figure, a clockwise traveling wave is generated on the diaphragm 2 of the two basic units (1U, 1D) when viewed from above, and the white in the figure. As shown by the pull-out arrow, the fluid supplied from the rear end side of the fluid transport path 9R is transported toward the front end side, and the fluid is discharged from the opening in front of the fluid transport path 9R. Of course, if the direction of the traveling wave is reversed, the fluid can be transported from the front to the rear. The partition walls (8C, 8R) are preferably formed of a easily deformable material such as an elastic body such as rubber so as not to attenuate the amplitude of the traveling wave.

The fluid transport device 210 shown in FIG. 10 is provided with one fluid transport path 9R and is configured to transport the fluid in one direction in the front-rear direction. However, as in the fluid transport device 310 shown in FIG. A partition wall 8L may be provided at the left end between the upper and lower two basic units (1U, 1D), and fluid transport paths (9L, 9R) may be formed on the left end side and the right end side of the layers, respectively. Thereby, one fluid transport path (9L, 9R) can transport the fluid in one direction in the front-rear direction, and the other fluid transport path (9R, 9L) can transport the fluid in the other direction. Then, for example, if a tube or the like is connected to the front and rear openings of the fluid transport paths (9R, 9L) on both the left and right sides, the fluid is transferred from the rear to the front by the fluid transport paths (9L, 9R) on one of the left and right sides. While transporting, the fluid can be transported from the front to the rear by the other fluid transport path (9R, 9L) on the left and right.

In the example shown in FIG. 11, as shown by the thick arrow in the figure, a clockwise traveling wave is generated on the diaphragm 2 of the two basic units (1U, 1D) when viewed from above, and the white in the figure. As shown by the pull-out arrow, the fluid transport path 9R on the right transports the fluid from the rear to the front, and the fluid transport path 9L on the left transports the fluid from the front to the rear.

=== Other Examples ===
The diaphragm 2 of the piezoelectric actuator 1 according to the embodiment shown in FIG. 1 is such that vibration in both the first vibration mode and the second vibration mode is likely to occur at a certain frequency (for example, 130 kHz). The ratio L: W of the length L to the width W was set to 5: 2. Of course, the ratio of the length L to the width W of the diaphragm 2 does not have to be exactly 5: 2. For example, when L: W = 5: 25, the diaphragm 2 generates a standing wave in the vibration mode that bends in the front-rear direction, which corresponds to the first vibration mode, at 67.8 kHz, and at 70.2 kHz. , A standing wave that is 180 ° out of phase in the left-right direction, which corresponds to the second vibration mode, is generated. However, the standing wave at 67.8 kHz is formed for 1.5 wavelengths with the front end 22 and the rear end 23 of the diaphragm 2 as free ends, and is fixed in the length direction at 70.2 kHz. The standing wave was formed for one wavelength with the front end 22 and the rear end 23 of the diaphragm 2 as free ends. In the piezoelectric actuator using the vibrating plate 2 with L: W = 5: 25, a traveling wave is generated at a frequency of 70 kHz, but the excitation region of the first vibration mode and the excitation region of the second vibration mode are one. The parts overlapped, and it was not possible to secure a sufficient area for the piezoelectric element in both regions, resulting in a small amplitude. That is, the traveling wave could not be generated efficiently. Therefore, for example, when a self-propelled device is configured by using this piezoelectric actuator, a sufficient propulsive force may not be obtained. In any case, it is necessary to configure the piezoelectric actuator by using the diaphragm 2 that can resonate in the first vibration mode shown in FIG. 3 and the second vibration mode shown in FIG.

As shown in FIGS. 1 and 2, the diaphragm 2 of the basic unit 1 is made of a conductive stainless steel plate, and the diaphragm 2 also serves as an electrode on the lower surface side of the piezoelectric element (3a, 3b). Was there. Of course, the diaphragm 2 can also be made of an insulator. Then, if a conductor pattern is formed on the upper surface of the vibrating plate 2 by printing or the like, and the lower surface of the piezoelectric body 31 and the upper surface of the conductor pattern are attached to each other by using a conductive adhesive or the like, the conductor pattern becomes a piezoelectric element (3a, It becomes an electrode on the lower surface side of 3b).

In the self-propelled device 110 shown as the second application example, the left and right basic units (1L, 1R) are the same, and the second piezoelectric element 3a is arranged along the left end 24 of the diaphragm 2. Of course, the second piezoelectric element of one of the left and right basic units 1 may be arranged along the right end 25 of the diaphragm 2. Alternatively, while using the same two basic units 1L, the self-propelled device may be configured by reversing the front-rear direction of one of the left and right basic units (1L, 1R) and the other left and right basic units (1R, 1L). good. In any case, the phases of the drive signals applied to the first piezoelectric element 3a arranged in the center of the left and right of the vibrating plate 2 and the second piezoelectric element 3b arranged along one of the left and right edges are appropriately set. By doing so, the traveling direction and the rotating direction of the self-propelled device 110 can be controlled.

1,1L, 1R, 1U, 1D Piezoelectric actuator (basic unit), 2 Vibrating plate, 3a, 3aL, 3aR 1st piezo element, 3b, 3bL, 3bR 2nd piezo element, 10 motor, 22 Front end of vibrating plate, 23 Rear end of vibrating plate, 24 left end of vibrating plate, 25 right end of vibrating plate, 30 drive circuit, 31 piezoelectric body, 32 signal electrode, 41, 42 excitation region, 110 self-propelled device, 210, 310 fluid transport device

Claims (4)

The first piezoelectric element and the second piezoelectric element are attached to one main surface of a rectangular planar vibrating plate in which the extension direction of the long side is the front-rear direction and the extension direction of the short side is the left-right direction.
The first piezoelectric element and the second piezoelectric element are formed by arranging electrode plates on both the front and back surfaces of a rectangular flat plate-shaped piezoelectric body.
The first piezoelectric element and the second piezoelectric element are arranged so as to be separated from each other in the front-rear direction of the diaphragm.
The diaphragm vibrates in the first vibration mode at the first resonance frequency and vibrates in the second vibration mode at the second resonance frequency.
In the first vibration mode, standing waves of two wavelengths are generated in the front-rear direction on the diaphragm with both front and rear ends as free ends.
In the second vibration mode, a standing wave for 1.5 wavelengths is generated in the front-rear direction with both front and rear ends as free ends, and at the position of the antinode of the standing wave for 1.5 wavelengths, the vibration plate With the left and right ends of the free end, standing waves of 1/2 wavelength are generated in the left and right direction.
The excitation region in the first vibration mode is a region between two adjacent nodes in the front-rear direction.
The first piezoelectric element is arranged at the center of the left and right in the excitation region on one of the front and rear of the first vibration mode.
The excitation region in the second vibration mode is an overlapping region between the region to the left or right with respect to the center of the left and right and the region between the nodes adjacent to each other in the front-rear direction in the standing wave in the front-rear direction.
The second piezoelectric element is arranged along the left or right edge of the diaphragm, in the front and rear other excitation regions in the second vibration mode, and has a width in the left-right direction of the diaphragm. It is less than 1/2 of the left and right width,
Piezoelectric actuator characterized by that. The piezoelectric actuator according to claim 1, wherein the left-right width of the first piezoelectric element is ½ or more of the left-right width of the diaphragm. A self-propelled device configured by using two piezoelectric actuators according to claim 1 or 2.
The two piezoelectric actuators are connected in a state of being arranged in parallel on the left and right sides with the one main surface side of the diaphragm as the upper surface.
Propulsion portions are formed in a region along the left edge of the lower surface of the diaphragm in the piezoelectric actuator on the left and a region along the right edge of the lower surface of the diaphragm in the piezoelectric actuator on the right.
A driving signal having a phase difference of 90 ° is applied to the first piezoelectric element and the second piezoelectric element to generate a traveling wave in the plane of the diaphragm.
The propulsion unit transmits the traveling wave to the mounting surface by frictional force.
A self-propelled device characterized by that. A fluid transport device configured by using two piezoelectric actuators according to claim 1 or 2.
The two piezoelectric actuators are laminated in the vertical direction.
The upper piezoelectric actuator has the one main surface as the upper surface.
The lower piezoelectric actuator has the one main surface as the lower surface.
Between the upper and lower layers of the piezoelectric actuator, a partition wall extending from the front end to the rear end is formed in a region in the center of the left and right and a region along at least one of the left and right edges.
A fluid transport path that opens at both front and rear ends is formed between the layers by the partition wall.
A drive signal having a phase difference of 90 ° is applied to the first piezoelectric element and the second piezoelectric element to generate a traveling wave that orbits in the same direction on the diaphragm of the piezoelectric actuator above and below.
A fluid transport device characterized by that.

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