JP3139150B2 - Piezoelectric resonator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator, and more particularly, to a piezoelectric resonator configured so that vibration energy of a piezoelectric resonance portion is confined in the piezoelectric resonator.

[0002]

2. Description of the Related Art Heretofore, as a piezoelectric resonator in the kHz band, a resonator utilizing a spreading vibration mode of a square plate-like piezoelectric plate, and a length mode vibration which expands and contracts in the length direction of a rod-like piezoelectric body have been used. The used resonator or the piezoelectric tuning fork resonator is used. By the way, since the piezoelectric resonator vibrates when a voltage is applied to the resonance portion, when the piezoelectric resonator is configured as an actual component, the piezoelectric resonator is supported so as not to interfere with resonance. There is a need to. However, in the energy-trap type piezoelectric resonator, the vibration energy of the resonance portion is confined, so that it is possible to mechanically retain the vibration energy in a region other than the resonance portion. Therefore, in consideration of application to a product, an energy trapping type piezoelectric resonator is easier to use, and therefore, an energy trapping type resonator is also required for a kHz-band piezoelectric resonator.

[0003]

However, it is impossible to confine vibration energy in a resonator using a spread vibration mode or a resonator using a length vibration mode, which is known as a general kHz-band piezoelectric resonator. Met. Therefore, as shown in FIG. 2A, in the piezoelectric resonator 91 using the length vibration mode, a structure is adopted in which the vibration resonance node 91 is held between the spring terminals 92 and 93 to hold the piezoelectric resonator 91. I was Similarly, in a square plate-shaped piezoelectric resonator using the expansion vibration mode, energy cannot be confined.
A structure of sandwiching and holding by a spring terminal has been adopted. Therefore, in the case of a piezoelectric resonator using a spreading vibration mode or a length vibration mode in the kHz band, the component structure is complicated, and it has been extremely difficult to configure a small chip-type component that can be surface-mounted.

On the other hand, as shown in FIG. 2B, slits 94a to 94c are formed in a piezoelectric plate 94 polarized in the thickness direction.
In the piezoelectric tuning fork resonator 96 in which the vibrating electrodes 95a (the back side is not shown) are formed on both main surfaces around the central slit 94b, energy is confined in the vibrating portion. Therefore, for example, the edge 94 of the piezoelectric plate 94
Even if held near d and 94e, the characteristics do not fluctuate, so that a chip component that can be surface-mounted can be configured.

However, in the piezoelectric tuning fork resonator 96, energy can be confined, but due to mode restrictions, a bandwidth of only about 2% of the resonance frequency can be secured. On the other hand, in the market, there is a strong demand for a broadband piezoelectric resonator even in the kHz band, and the piezoelectric tuning fork resonator 96 cannot meet such a demand. An object of the present invention is to provide an energy-trap type piezoelectric resonator that can be used in the kHz band and that can obtain a wider band characteristic.

[0006]

According to the present invention, there is provided a piezoelectric resonance unit having a piezoelectric body and a plurality of excitation electrodes formed on the piezoelectric body, the piezoelectric resonance unit being excited in a predetermined vibration mode, and one end being provided with the piezoelectric resonance unit. a vibration transmitting portion connected to the resonant unit, the vibrating
A rectangular plate extending in the direction intersecting with the direction in which the transmission section extends
It has a shape, is connected to a portion other than the node of the vibration of the vibration transmitting unit when vibrated by the vibration propagated from the piezoelectric resonance unit, and receives the vibration of the piezoelectric resonance unit to cancel the vibration. characterized in that it comprises a said piezoelectric resonator unit, which is configured to resonate at at bending vibration mode resonant frequency and substantially the same frequency of the resonance unit is a piezoelectric resonator.

[0007]

According to the piezoelectric resonator of the present invention, the vibration in the piezoelectric resonance unit is transmitted to the resonance unit via the vibration transmission unit. The resonance section is connected to a portion other than the node point of the vibration transmission section, and has a bending vibration at a frequency substantially equal to the resonance frequency of the piezoelectric resonance unit due to the vibration propagated through the vibration transmission section. It is configured to resonate in the mode. Therefore, as is apparent from the examples described later, because the displacement vector in the vibration transmission unit cancels the displacement vector in the resonance unit, the propagated vibration is hardly transmitted outside the resonance unit, and it is as if to the resonance unit. It operates in such a state that vibration energy is confined in the part.

Therefore, by adopting an appropriate structure such as a piezoelectric resonance unit using a length vibration mode or a piezoelectric resonance unit using a spreading vibration mode of a square plate as the piezoelectric resonance unit, the kHz band or several MHz is adopted. It is possible to realize a wide-band energy trap type piezoelectric resonator that can be used in a band.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram schematically showing a piezoelectric resonator according to the present invention. In the piezoelectric resonator of the present invention, the vibration transmitting unit 1b is connected to the piezoelectric resonance unit 1a, and the resonance unit 1c is connected to a portion other than the node point of the vibration transmitting unit 1b.
Are connected. The piezoelectric resonance unit 1a is configured to be able to be excited in an appropriate vibration mode such as a length vibration mode, a spreading vibration mode, or the like, as will be apparent from embodiments described later. Further, the vibration transmitting unit 1b is provided to transmit the vibration propagated from the piezoelectric resonance unit 1a to the resonance unit 1c. Therefore, the structure itself of the vibration transmission unit 1b is not particularly limited as long as it supports the piezoelectric resonance unit 1a and can transmit vibration to the resonance unit 1c.

The resonance section 1c receives the vibration propagated via the vibration transmission section 1b and receives the vibration.
Is configured to resonate in the bending vibration mode at a frequency substantially the same as the resonance frequency of. The resonating portion 1c acts to cancel the propagated vibration by resonance, as will be described later in experimental examples and examples. In the energy trap type piezoelectric resonator according to the present invention, the transmitted vibration is canceled by the resonance portion 1c, thereby preventing or suppressing the leakage of the vibration to the outside of the device. Such leakage or suppression of the vibration by the resonating portion has been found by accident by the inventors of the present application. Hereinafter, FIG.
This will be described more specifically with reference to FIGS.

FIG. 3 is a front sectional view showing an experimental apparatus for clarifying the principle of the present invention. Referring to FIG.
A support rod 4 is provided upright on the upper surface of the vibration testing machine 3.
A steel rod 5 capable of vibrating in a bending vibration mode is fixed at an intermediate height position of the support rod 4. The steel bar 5 has a length of 18
It is a rod-shaped member made of steel having a size of 0 mm x 12 mm x 15 mm, weighs 240 g, and has a resonance frequency of about 1 kHz when bent. On the other hand, the support rod 4 is a columnar member made of steel having a diameter of 8 mm, is inserted into a through hole provided at the center of the steel rod 5, and the steel rod 5 and the support rod 4 are shown in the drawing. The state is fixed. Therefore, the vibration testing machine 3 corresponds to the piezoelectric resonance unit of the present invention, the steel bar 5 corresponds to the resonance unit, and the portion of the support rod 4 below the steel bar 5 corresponds to the vibration transmission unit.

When the vibration testing machine 3 was vibrated at a frequency of 1 kHz in the vertical direction as shown by the arrow in the figure, the steel rod 5
Resonated in the bending vibration mode, and the amount of displacement of the upper end 4a of the support rod 4 was as shown in FIG. In FIG. 4, the amount of displacement ΔB was about 2.6 μm. For comparison, when the support rod 4 was erected on the vibration tester 3 without the steel bar 5 and the vibration tester 3 was similarly vibrated, the displacement of the upper end 4a of the support rod 4 was As shown in FIG.
The displacement ΔA in the figure was about 22.6 μm.

As is clear from the comparison between FIG. 4 and FIG.
It can be seen that the vibration transmitted from the vibration tester 3 via the support rod 4 is sufficiently attenuated at the steel rod 5 by providing the steel rod 5. The inventors of the present application also considered that the vibration was damped by the mass of the steel rod 5 and changed the frequency of the applied vibration and performed an experiment without causing the steel rod to resonate. It was confirmed that the displacement amount in 4a was not suppressed as shown in FIG. That is, as is apparent from this, the transmitted vibration is not simply damped by the weight of the steel rod 5, but the transmitted vibration is canceled by the steel rod 5 as described above. it is conceivable that.

As described above, the vibration tester 3 as a vibration source
On the other hand, since the steel rod 5, that is, the resonator is connected via the support rod 4 arranged to receive the vibration of the vibration testing machine 3, the transmitted vibration is canceled in the resonator. That is, in the piezoelectric resonator according to the present invention, the transmitted vibration is canceled by the resonance unit, so that the vibration energy of the piezoelectric resonance unit can be confined in the device. Next, the operation of the resonance unit will be described based on a more specific embodiment, thereby clarifying the present invention.

The piezoelectric resonator of the embodiment using the length vibration mode
FIGS. 6A and 6B are a plan view showing a piezoelectric resonator according to the first embodiment of the present invention and a plan view showing the shape of an electrode on a lower surface through a piezoelectric substrate. The piezoelectric resonator 21 has a piezoelectric resonance unit 22 disposed at the center. The piezoelectric resonance unit 22 has a structure in which electrodes 22a and 22b are formed on both main surfaces of a rectangular piezoelectric ceramic substrate having a slender planar shape that is uniformly polarized in the thickness direction. Electrode 22
The piezoelectric resonance unit 22 is configured to expand and contract in a length vibration mode by applying an AC voltage from the terminals a and 22b.

A vibration transmission section 23 is connected to one side of the piezoelectric resonance unit 22 at the center in the length direction.
The vibration transmission unit 23 is provided to transmit vibration accompanying expansion and contraction vibration of the piezoelectric resonance unit 22 to a resonance unit 24 described below. Further, the vibration transmission unit 23 is
Is connected to the central portion in the length direction in order to prevent the vibration of the piezoelectric resonance unit 22 as much as possible.

The other end of the vibration transmitting portion 23 receives a vibration of the piezoelectric resonance unit 22 and resonates at a frequency substantially equal to the resonance frequency of the piezoelectric resonance unit 22 and in a bending vibration mode. The part 24 is connected. Note that the other end of the vibration transmitting unit 23, that is, the portion to which the resonance unit 24 is connected is a portion other than the node point of the vibration transmitting unit 23. In addition, the resonance bar 24 includes a connection bar 25.
The holding portion 26 having a relatively large area is connected via the. The holding portion 26 is configured to have a relatively large area as shown in the drawing so as to be suitable for mechanically holding the piezoelectric resonator 21 on another member such as a case substrate.

The electrode 22a is electrically connected to a terminal electrode 28a formed on the upper surface of the holding section 26 by a connection conductive section 27a. Also on the side opposite to the side to which the vibration transmitting unit 23 is connected, the vibration transmitting unit 29, the resonance unit 30, the connection bar 31, and the holding unit 3 are attached to the piezoelectric resonance unit 22.
2 are connected to each other, and have the same configuration as the vibration transmission unit 23 side. However, as shown in FIG. 6B, the connection conductive portion 27b and the terminal electrode 28b electrically connected to the electrode 22b are respectively connected to the vibration transmission portion 29 and the resonance portion 3
0, the connecting bar 31 and the holding portion 32 are formed on the lower surface side.

In the piezoelectric resonator 21 of this embodiment, when an AC voltage is applied between the terminal electrodes 28a and 28b, the piezoelectric resonance unit 22 expands and contracts in a length vibration mode. As a result, the vibration is transmitted to the vibration transmitting units 23 and 29.
Is transmitted to the resonance units 24 and 30 via the. Then, as described with reference to FIGS. 7 and 8, the vibration hardly leaks to the connection bars 25 and 31 because the displacement vector in the vibration transmission unit and the displacement vector in the resonance unit cancel each other. Therefore, the vibration energy is confined in the portion up to the resonance parts 24 and 30. Therefore, when mechanically fixed to the outside using the holding parts 26 and 32, the energy confinement type using the length vibration mode is used. The piezoelectric resonator 21 can be realized.

As described above, by connecting the resonance units 24 and 30 to the piezoelectric resonance unit 22 via the vibration transmitting units 23 and 29, it is possible to confine energy based on the resonance of the piezoelectric resonance unit. It was discovered by accident by these experiments that the resonance part 24,
The following mechanism is considered to be able to confine the vibration transmitted by 30.

As the mechanism capable of confining the vibration transmitted as described above, there are two types of mechanisms described with reference to FIGS. 7 and 8 below. That is, FIG.
As is apparent from FIG. 2, for example, a resonance portion 24 is connected to the outside of the vibration transmission portion 23. The resonance portion 24 has a pair of resonance portions with cantilever beams on both sides of a portion where the vibration transmission portion 23 is extended. It can be considered that the structure is a connected structure, or a structure in which one resonance part 24 is interposed between the vibration transmission part 23 and the connection bar 25. FIG. 7 is a schematic enlarged plan view for explaining the operation of the resonance section based on the former structure, and FIG.
FIG. 4 is a schematic enlarged plan view for explaining the operation of the resonance unit based on the latter structure.

First, it is assumed that a pair of resonating portions are formed on both sides of a portion where the vibration transmitting portion is extended, and the operation of the resonating portions will be described with reference to FIG. Now, it is assumed that there is a vibration transmitting portion 23a connected to the piezoelectric resonance unit. In this case, when the piezoelectric resonance unit expands and contracts, the transmitted vibration causes the vibration transmitting unit 23a to generate the reference numeral 23b.
And a state indicated by reference numeral 23c is repeated. By the way, assuming that the resonance units 24a and 24b are connected to the vibration transmission unit, the resonance units 24a and 24b are connected to the vibration transmission unit 23 as shown in FIG.
As shown in the figure, it resonates with the deformation of b and 23c and resonates. As a result, the displacement vector in each of the inclined resonance parts 24a and 24b becomes the direction shown by the arrow A in the figure.

On the other hand, the X in the vibration transmitting portion 23b shown in FIG.
The displacement vector in the axial direction is as shown by arrow B. Therefore, in any state, X
The displacement vector along the axial direction and the displacement vector along the X-axis direction of the vibration transmitting unit are in a direction in which they cancel each other. Therefore, it is considered that the vibration transmitted through the vibration transmitting unit is canceled by the resonance of the resonance units 24a and 24b, so that the vibration energy is confined to the portions up to the resonance units 24a and 24b.

On the other hand, one resonance section 2 is connected to the other end of the vibration transmission section.
FIG. 8 shows a mechanism in a case where the central portion of
This will be described with reference to FIG. Now, it is assumed that there is a vibration transmitting portion 23a connected to the piezoelectric resonance unit. In this case, when the piezoelectric resonance unit expands and contracts, the transmitted vibration causes the vibration transmission unit to deform so as to repeat the state indicated by reference numeral 23b and the state indicated by reference numeral 23c.

The other end of the vibration transmitting section is connected to the resonance section 2.
In the case where 4 is connected at the center, as shown in FIG. 8, the resonating unit 24 bends and vibrates as shown in FIG. As a result, the displacement vector in the resonance section 24 is as shown in the figure. That is, as in the case shown in FIG. 7, the displacement vector B in the portion where the vibration transmitting portions 23b and 23c are extended and the displacement vector A in the remaining portion of the resonance portion 24 cancel each other out in the X-axis direction. balance. Therefore, it is considered that the vibration propagating through the vibration transmitting unit is canceled with the resonance of the resonance unit 24, so that the vibration energy is confined to the portion up to the resonance unit 24.

The above two types of vibration energy confinement mechanisms are based on estimation, but in any case, as shown in FIG. The vibration transmitted through the transmission unit 23 is canceled by the resonance unit 24, thereby confining the vibration energy. The operation of the resonance unit 24 will be described based on specific experimental results.

FIG. 9 shows a structure prepared for comparison. The piezoelectric resonance unit 35 is configured to be able to vibrate in the length vibration mode. An extending bar 36 is connected. The bar 36 is similarly connected to the center of the other side surface. On the other hand, FIG. 10 has a structure in which the resonance section 37 is provided in the structure shown in FIG. That is, FIG.
In the structure of FIG.
And a bar 39 is connected to the surface of the resonance unit 37 opposite to the side to which the vibration transmission unit 38 is connected. In other words, the vibration transmission unit 3
8 and the bar 39, the resonance portion 37
Corresponds to the structure formed with. In the structure of FIG. 10,
The same structure as described above is connected to the other side surface of the piezoelectric resonance unit 35.

When the piezoelectric resonator unit 35 is vibrated in the length vibration mode in the piezoelectric resonator shown in FIG. 9, the displacement distribution is as shown in FIG. the absolute value of the displacement amount V _x in the X-axis direction at each portion is as shown in FIG. 11 (b). On the other hand, the displacement distribution of the vibration when the piezoelectric resonance unit 35 is resonated in the piezoelectric resonator shown in FIG. 10 is as shown in FIG. The absolute value V _x in the X-axis direction displacement at each portion on the X axis in FIG. 12 was as shown in FIG. 14.

As is apparent from a comparison between FIG. 11B and FIG. 14, the provision of the resonance
It can be seen that the displacement amount due to the transmitted vibration is very small in the bar 39 before the bar 7. In other words, it is understood that the vibration energy can be effectively confined in the portion up to the resonance portion 37. Next, when the resonance frequency of the piezoelectric resonance unit and the resonance frequency of the resonance unit are made substantially the same, the fact that the vibration energy can be effectively confined to the portion up to the resonance unit as described above is shown in FIGS. FIG.
This will be described with reference to FIG.

As described above, when the piezoelectric resonance unit 35 is vibrated in the structure shown in FIG. 10, the displacement distribution is as shown in FIG. The displacement distribution shown in FIG.
Shows the displacement distribution when each resonates with the fundamental wave.
Now, as the piezoelectric resonance unit 35, a piezoelectric resonance unit having a width of 0.6 mm, a length of 4.0 mm and a thickness of 0.4 mm and a resonance frequency of 422 kHz is used, and the width W and the length l of the resonance part 37 (FIG. 10). Figure 1)
FIGS. 13 to 18 show the absolute value of the displacement amount in the X direction at each portion along the X axis direction of FIG.

FIGS. 13 to 15 show that the length 1 of the resonance part 37 is 0.70 mm and the width W is 0.55, 0.6, respectively.
5 and 0.75 mm, the displacement amounts are shown.
16 to 18 show displacement amounts when the width W is 0.65 mm and the length 1 is 0.65, 0.70, and 0.75 mm, respectively. The reason why the length 1 and the width W of the resonance section 37 are changed as described above is to change the resonance frequency of the resonance section 37.

The data of FIG. 13 and FIG.
As is clear from comparison with the displacement data shown in
It can be seen that the transmitted vibration energy can be canceled for the time being even when the resonance section 37 is provided in any of the above dimensions. However, it can be seen that in the structures of FIGS. 14 and 17, the vibration energy propagated by the action of the resonance section 37 is more effectively canceled. This is thought to be because the resonance frequency of the piezoelectric resonance unit 35 and the resonance frequency of the resonance unit 37 are substantially the same, so that the transmitted vibration energy is effectively canceled by the resonance in the resonance unit 37. .

Next, the operation of the resonance section in the case of using the third harmonic of the piezoelectric resonance unit 35 and the resonance section 37 in the structure shown in FIG. 10 will be described. FIG. 19 shows displacement distributions when the piezoelectric resonance unit 35 resonates at the third harmonic and when the resonance unit 37 resonates at the third harmonic in the bending vibration mode. In this case, the piezoelectric resonance unit 35 has a length of 4.0 mm, a width of 0.6 mm, and a thickness of 0.4 mm.
(The third harmonic having a resonance frequency of 1.237 kHz) was used. Then, the length 1 of the resonance section 37 is set to 0.70
mm, and the width W is 0.55 mm and 0.65 mm, respectively.
The absolute values of the displacement along the X-axis direction when mm and 0.75 mm are shown in FIGS.

As is apparent from the comparison between FIGS. 20 to 22, the reason is that the resonance energy of the piezoelectric resonance unit 35 and the resonance frequency of the resonance part 37 match in the case of FIG. It is most effectively counteracted by the action. Next, with reference to FIGS. 23 to 26, the resonance section 37 is utilized by utilizing the resonance of the fundamental wave of the piezoelectric resonance unit 35.
The case of using the third harmonic will be described.
FIG. 23 is a diagram in which the displacement distribution in this case is measured by the finite element method.

Assume that the piezoelectric resonance unit 35 has a length of 1.6 mm, a width of 0.6 mm and a thickness of 0.4 mm, and has a resonance frequency of 1.072 kHz. And as the resonance part 37, the width W is set to 1.0 mm, and the length 1 is set to 0.65 mm and 0.70 mm, respectively.
24 to 26 show the absolute values of the displacement amounts along the X-axis direction in the case of 0.75 mm and 0.75 mm. As is clear from the comparison of FIGS. 24 to 26, in FIG. 25, the resonance frequency of the fundamental wave of the piezoelectric resonance unit 35 and the resonance frequency of the third harmonic of the resonance unit 37 match. The transmitted vibration energy is effectively canceled by the action of the resonance section 37. As described above, it can be seen that the resonance frequency at which the piezoelectric resonance unit and the resonance unit are to resonate may be any of the fundamental wave and the harmonic.

In the present invention, the resonance section is connected to a portion other than the node point of the vibration transmission section. For this reason, the transmitted vibration is more effectively canceled by the resonance unit. This will be described with reference to FIGS. When the piezoelectric resonance unit 35 resonates in the structure shown in FIG. 9, the vibration leaks to the bar 36. In this case, the displacement vector in the bar 36 is as shown in FIG. That is, the bar 36 is displaced by the propagated vibration (longitudinal wave) as shown in FIG. 27 (arrows in FIG. 27 indicate displacement vectors).

As is apparent from FIG. 27, the bar 36 has a portion that is largely displaced and a portion that is hardly displaced, that is, a node point, due to the transmitted vibration. That is, the relative scale in the X-axis direction shown in the upper part of FIG.
It can be seen that there is almost no displacement in the portion of No. 5. Therefore, in the piezoelectric resonator shown in FIG. 10, the operation of the resonance unit 37 was confirmed by changing the distance P, that is, the distance between the side surface of the piezoelectric resonance unit 35 and the center of the resonance unit 37.

FIGS. 28 to 31 respectively show the distance P
Are set to 0.5, 1.0, 1.5, 2.0,... And the absolute value of the displacement amount in the X-axis direction at each portion along the X-axis direction. As is clear from FIG. 30, the distance P = 1.5
In the case of, it can be seen that a considerable amount of vibration is propagated outside the resonating portion. This is the distance P = 1.5
When the resonance unit is connected to the position, that is, the node point,
This means that the vibration cannot be canceled sufficiently by resonance. In contrast, in FIG. 28 (when the distance P = 0.5), FIG. 29 (when the distance P = 1.0), and FIG. It can be seen that the leakage of the vibrations is very small. Therefore, in the present invention, it is preferable that the resonating portion is connected to a portion other than the node point of the vibration transmitting portion, so that the vibration propagated by the resonating portion can be effectively canceled.

As is apparent from a comparison between FIG. 11B and FIG. 30, even when the resonance section 37 is connected to the node point, FIG. In comparison with the piezoelectric resonator, the suppression of leakage of vibration to the outside can be achieved. In addition, in the piezoelectric resonator 21 of the embodiment shown in FIG.
Although the holding portions 26 and 32 are connected via 31, this is merely provided for facilitating mechanical fixing at the time of commercialization. That is, as shown in FIG. 32, connecting portions 40a and 40b for connecting with other portions are formed on the side of the resonance portions 24 and 30 opposite to the side where the vibration transmitting portions 23 and 29 are connected. In other words, as in the case of the embodiment shown in FIG. 6, the vibration energy can be confined in the portion up to the resonance portions 24 and 30. Therefore, as in the embodiment shown in FIG. Can be used as

The piezoelectric resonator 2 of the embodiment shown in FIG.
In FIG. 1, one resonating section 24, 30 is disposed on each side of the piezoelectric resonance unit 22, but as shown in FIG. 33, a plurality of resonating sections 24, 24 are disposed on both sides of the piezoelectric resonance unit 22, respectively. , 24,30,30,30
May be arranged. In this case, the vibration transmitting parts 23a and 23a
b, 31a and 31b.

For a piezoelectric resonator using a spreading vibration mode,
Example of with Figure 34 (a), (b) is a plan view showing the lower electrode watermark plan view and a piezoelectric plate of a piezoelectric resonator according to the second embodiment. The second embodiment is a piezoelectric resonator using a spread vibration mode of a square plate. Piezoelectric resonator 81
Has a piezoelectric resonance unit 82 utilizing a spread vibration mode of a square plate. The piezoelectric resonance unit 82 has a structure in which electrodes 82a and 82b are formed on the entire surfaces of both main surfaces of a square plate-shaped piezoelectric ceramic plate, and a portion of the piezoelectric ceramic plate sandwiched between the electrodes 82a and 82b is one in the thickness direction. It is polarized.

The second embodiment is characterized in that the above-described piezoelectric resonance unit 82 utilizing the expansion vibration mode is used as the piezoelectric resonance unit. In other respects, the piezoelectric resonance unit 82 of the first embodiment is used. It is configured similarly to the child 21. Therefore, in the piezoelectric resonator 81 shown in FIG. 34, the portions corresponding to those of the piezoelectric resonator 21 of the first embodiment shown in FIG. .

In the piezoelectric resonator 81, the terminal electrodes 28a, 2
By applying an AC voltage between 8b, the piezoelectric resonance unit 82 resonates in a spread vibration mode. And
Also in this embodiment, the vibration of the piezoelectric resonance unit 82 is
The vibration is transmitted to the resonance units 24 and 30 connected to portions other than the node points of the vibration transmission unit via the vibration transmission units 23 and 29,
The resonance portions 24 and 30 resonate in the bending vibration mode at a frequency substantially equal to the resonance frequency of the piezoelectric resonance unit. Therefore, the transmitted vibration is canceled by the resonance of the resonance units 24 and 30, and the vibration energy is confined in the portion up to the resonance units 24 and 30.

In the piezoelectric resonator 81 shown in FIG. 34, the resonance sections 24 and 3 are provided on both sides of the piezoelectric resonance unit 82.
0 is connected via the vibration transmitting units 23 and 29, but also in the vertical direction in the drawing of the piezoelectric resonance unit 82, a resonating unit capable of resonating in a bending vibration mode is similarly connected via the vibration transmitting unit. You may. As described above, in the piezoelectric resonator of the present invention, as the piezoelectric resonance unit, a piezoelectric resonance unit capable of resonating in various vibration modes can be used, and by connecting the resonance unit via the vibration transmission unit, Vibration energy can be reliably confined to the portion up to the resonance section. Therefore, it is possible to obtain an energy-trapping type piezoelectric resonator utilizing a vibration mode in which vibration energy cannot be confined conventionally.

[0045]

According to the present invention, a resonance unit that resonates at substantially the same frequency as the piezoelectric resonance unit is connected to the piezoelectric resonance unit via the vibration transmission unit and to a portion other than the node point of the vibration transmission unit. Therefore, the vibration propagated through the vibration transmission unit is canceled by the resonance in the resonance unit. Therefore, it is possible to effectively prevent the vibration from leaking to a portion connected to the outside of the resonance portion. In other words, the vibration energy is confined to the portion up to the resonance section.

Therefore, an energy trapping type piezoelectric resonator can be constituted by using a vibration mode piezoelectric resonance unit which has conventionally been considered impossible to constitute an energy trapping type piezoelectric resonator. Therefore, if the piezoelectric resonator of the present invention is configured using a piezoelectric resonance unit utilizing a length vibration mode or a square plate expansion vibration mode, an energy trapping type piezoelectric resonance that can be used in a kHz band or a few MHz band is used. It is possible to provide a piezoelectric resonator that is a child and has a wide band.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a configuration of the present invention.

FIGS. 2A and 2B are a perspective view and a plan view, respectively, showing a piezoelectric resonator and a piezoelectric tuning fork resonator using a conventional length vibration mode.

FIG. 3 is a front sectional view showing a test apparatus for explaining the principle of the present invention.

FIG. 4 is a diagram illustrating a relationship between a displacement amount and time in the test apparatus illustrated in FIG. 3;

FIG. 5 is a diagram showing a relationship between a displacement amount and time when no resonator is provided.

FIGS. 6A and 6B are a plan view of the piezoelectric resonator of the first embodiment and a schematic plan view showing a lower electrode shape through a piezoelectric plate, respectively.

FIG. 7 is a schematic diagram for explaining one possible mechanism of the operation of the resonance unit in the first embodiment.

FIG. 8 is a schematic diagram for explaining another mechanism of the operation of the resonance unit in the first embodiment.

FIG. 9 is a plan view showing a structure in which a bar is connected to a piezoelectric resonance unit using a length vibration mode.

FIG. 10 is a plan view having a structure in which a resonance unit is connected to a piezoelectric resonance unit using a length vibration mode.

11A and 11B are diagrams showing a displacement distribution in the structure shown in FIG. 9 and a diagram showing an absolute value of a displacement amount in each portion along the X-axis direction, respectively.

FIG. 12 is a view showing a displacement distribution in the structure shown in FIG. 10;

FIG. 13 is a view illustrating a state in which vibration energy based on the resonance of the fundamental wave of the piezoelectric resonance unit is transmitted to the resonance unit, and the resonance unit resonates with the vibration of the fundamental wave in the bending vibration mode along the X-axis direction. The figure which shows the absolute value of the displacement amount of the X-axis direction in each part.

FIG. 14 illustrates a case where the resonance frequency of the piezoelectric resonance unit matches the resonance frequency of the resonance unit, and the X in each part along the X-axis direction when the two resonate with the fundamental wave.
The figure which shows the absolute value of the displacement amount of an axial direction.

FIG. 15 is a diagram illustrating an absolute value of a displacement amount in the X-axis direction at each portion along the X-axis direction when the piezoelectric resonance unit and the resonance unit resonate with a fundamental wave.

FIG. 16 is a diagram showing an absolute value of a displacement amount in the X-axis direction in each portion along the X-axis direction when the piezoelectric resonance unit and the resonance unit resonate with a fundamental wave.

FIG. 17 is a diagram illustrating an absolute value of a displacement amount in the X-axis direction in each portion along the X-axis direction when the piezoelectric resonance unit and the resonance unit resonate with a fundamental wave.

FIG. 18 is a diagram illustrating an absolute value of a displacement amount in the X-axis direction in each portion along the X-axis direction when the piezoelectric resonance unit and the resonance unit resonate with a fundamental wave.

FIG. 19 shows that both the piezoelectric resonance unit and the resonance unit
The figure which shows the displacement distribution at the time of resonating by a second harmonic.

FIG. 20 is a diagram showing the absolute value of the displacement along the X-axis direction in each portion along the X-axis direction when the piezoelectric resonance unit and the resonance section resonate as shown in FIG. 19;

FIG. 21 is a diagram showing the absolute value of the displacement along the X-axis direction at each portion along the X-axis direction when the piezoelectric resonance unit and the resonance section resonate as shown in FIG. 19;

FIG. 22 is a view showing the absolute value of the displacement along the X-axis direction in each portion along the X-axis direction when the piezoelectric resonance unit and the resonance section resonate as shown in FIG. 19;

FIG. 23 is a diagram illustrating a displacement distribution in a case where the piezoelectric resonance unit resonates with a fundamental wave and the resonance unit vibrates with a third harmonic of vibration in a bending vibration mode.

FIG. 24 is a diagram illustrating an absolute value of a displacement amount along the X-axis direction in each portion along the X-axis direction when the piezoelectric resonance unit resonates with the fundamental wave and the resonance unit resonates with the third harmonic.

FIG. 25 is a diagram showing an absolute value of a displacement amount along the X-axis direction in each portion along the X-axis direction when the piezoelectric resonance unit resonates with the fundamental wave and the resonance unit resonates with the third harmonic.

FIG. 26 is a diagram illustrating an absolute value of a displacement amount along the X-axis direction in each portion along the X-axis direction when the piezoelectric resonance unit resonates with the fundamental wave and the resonance unit resonates with the third harmonic.

FIG. 27 is a diagram showing a displacement state of a vibration transmission unit in the structure shown in FIG. 10;

FIG. 28 is a diagram showing the absolute value of the displacement amount in the X-axis direction in each portion along the X-axis direction when the distance P = 0.5 in FIG. 10;

FIG. 29 is a diagram showing the absolute value of the displacement amount in the X-axis direction at each portion along the X-axis direction when the distance P = 1.0 in FIG. 10;

FIG. 30 is a diagram showing the absolute value of the displacement amount in the X-axis direction at each portion along the X-axis direction when the distance P in FIG. 10 is 1.5 (in the case of a node point).

FIG. 31 is a diagram showing the absolute value of the displacement amount in the X-axis direction at each portion along the X-axis direction when the distance P = 2.0 in FIG. 10;

FIG. 32 is a plan view showing a modification of the piezoelectric resonator of the first embodiment.

FIG. 33 is a plan view showing another modified example of the piezoelectric resonator of the first embodiment, showing a structure in which a plurality of resonance sections are arranged.

FIGS. 34A and 34B are a plan view of the piezoelectric resonator of the second embodiment and a plan view showing the shape of the lower electrode seen through the piezoelectric plate, respectively.

[Explanation of symbols]

 1a: Piezoelectric resonance unit 1b: Vibration transmission unit 1c: Resonance unit

Continuation of front page (56) References JP-A-2-207614 (JP, A) JP-A-1-241210 (JP, A) JP-A 1-222913 (JP, A) JP-A-55-121728 (JP) JP-A-55-85120 (JP, A) JP-A-54-51498 (JP, A) JP-A-4-49707 (JP, A) JP-A-3-284007 (JP, A) 3-265209 (JP, A) JP-A-3-108810 (JP, A) JP-B-45-36780 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 9/00 -9/215

Claims (1)

(57) [Claims] 1. A piezoelectric resonance unit having a piezoelectric body and a plurality of excitation electrodes formed on the piezoelectric body, the piezoelectric resonance unit being excited in a predetermined vibration mode, and having one end connected to the piezoelectric resonance unit. Part, and a rectangle extending in a direction intersecting with a direction in which the vibration transmitting part extends.
It has a plate-like shape, is connected to a portion other than the node point of the vibration of the vibration transmission unit when vibrated by the vibration propagated from the piezoelectric resonance unit, and receives the vibration of the piezoelectric resonance unit. A resonator configured to resonate in a bending vibration mode at a resonance frequency substantially equal to the resonance frequency of the piezoelectric resonance unit so as to cancel the vibration.