JP3870770B2 - Piezoelectric sliding resonator and composite vibration device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric sliding resonator and a composite material vibration device. More specifically, the present invention relates to a piezoelectric sliding resonator used as a vibration member of a composite material vibration device, and is not an energy confining type while using the piezoelectric sliding resonator as a vibration member. It is related with the composite-material vibration apparatus comprised.
[0002]
[Prior art]
Among piezoelectric resonators used as piezoelectric resonators and band-pass filters (BPF), those disclosed in Japanese Patent Laid-Open Nos. 5-2443889 and 7-147527 are disclosed. is there. That is, the thickness-slip piezoelectric vibration element disclosed in Japanese Patent Application Laid-Open No. 5-243889 has excitation electrodes formed on both main surfaces of a piezoelectric substrate made of LiTaO ₃ , and is unnecessary in the vicinity of the resonance frequency. In order to suppress the ripples, the relationship between the length of the excitation electrodes facing each other and overlapping each other and the thickness of the piezoelectric substrate is regulated within an appropriate range.
[0003]
On the other hand, the piezoelectric resonator disclosed in JP-A-7-147527 is formed by opposing resonant electrodes on both major surfaces on the long side of a piezoelectric body having a rectangular surface. It is characterized by regulating the length ratio of the long side and the short side in relation to the Poisson's ratio. And if it is a piezoelectric resonator of such a structure, it will become possible to improve the energy confinement efficiency of a resonance part by adopting a specific length ratio, and the advantage that the miniaturization can be realized is secured. Is done.
[0004]
[Problems to be solved by the invention]
By the way, what is disclosed in Japanese Patent Laid-Open No. 5-2443889 is a piezoelectric sliding resonator called a normal energy confinement type. In the case of such an energy confinement type configuration, a specific band (passband width) is disclosed. It becomes difficult to construct a thickness-slip resonator having a large (center frequency). In addition, normal energy confinement refers to a vibration phenomenon in which vibration energy is locally concentrated near the overlapping part of the excitation electrodes. In the piezoelectric sliding resonator having the above configuration, the vibration part extends from the vibration part to the non-vibration part. Since a large area is required to configure the region, that is, the vibration attenuation region, it is not suitable for downsizing.
[0005]
On the other hand, the piezoelectric sliding resonator disclosed in Japanese Patent Laid-Open No. 7-147527 is also an energy confinement type. However, since the energy confinement efficiency is greatly improved, compared with a normal energy confinement type. Therefore, it is possible to realize the miniaturization. However, even in the case of a piezoelectric sliding resonator having such a configuration, the actual bandwidth cannot be increased.
[0006]
The present invention was devised in view of these disadvantages, and is a piezoelectric sliding resonator capable of increasing the specific band, and a composite that can achieve downsizing while using this piezoelectric sliding resonator as a vibrating member. The object is to provide a material vibration device. Note that the composite material vibration device here is not configured to be an energy confinement type.
[0007]
[Means for Solving the Problems]
The piezoelectric sliding resonator according to claim 1 of the present invention includes a prismatic piezoelectric body that excites a sliding vibration mode, and the rectangular displacement strain surface has a vertical dimension T as the displacement strain surface. The aspect ratio Le / T when the horizontal dimension is Le is
Le / T = {α · (S44E / S33E) 1/2 + β} ± 0.3
(However, S44E and S33E are elastic compliances, α = 0.27 · n + 0.45, β = 1.09 · n + 0.31, n is a positive integer)
It is represented by.
[0009]
A piezoelectric sliding resonator according to a second aspect of the present invention is the piezoelectric sliding resonator according to the first or second aspect, wherein both principal surfaces are orthogonal to the displacement strain surface and parallel to the displacement direction of the piezoelectric body. Excitation electrodes are formed above, and the ratio L / Le of the length L where the opposing excitation electrodes overlap each other and the lateral dimension Le of the displacement strain surface is:
0.86 ≦ L / Le ≦ 1
It is characterized by being expressed.
[0010]
A piezoelectric sliding resonator according to a third aspect of the present invention is the piezoelectric slip resonator according to the first or second aspect, wherein a ratio between a gap W between the offset strain surfaces facing each other and a vertical dimension T of the offset strain surface. W / T is
(1) W / T ≦ 1.2
(2) 1.3 ≦ W / T ≦ 1.5
(3) 1.7 ≦ W / T ≦ 2.0
(4) 2.2 ≦ W / T ≦ 2.5
(5) 2.6 ≦ W / T ≦ 3.0
It is characterized by being expressed in either of these.
[0011]
A composite material vibration device according to a fourth aspect of the present invention uses the piezoelectric sliding resonator according to any one of the first to third aspects as a vibration member, and a vibration member whose acoustic impedance is Z1, A second acoustic impedance Z2 lower than the first acoustic impedance Z1, a reflective layer connected to the vibrating member, and a third acoustic impedance Z3 higher than the second acoustic impedance Z2, And a holding member connected to the reflective layer, wherein the vibration propagated from the vibrating member to the reflective layer is reflected at the interface between the reflective layer and the holding member.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
(Embodiment 1)
FIG. 1 is a perspective view showing a simplified configuration of a piezoelectric sliding resonator according to the present embodiment, and FIG. 2 is an explanatory diagram showing a relationship between an aspect ratio Le / T of a slipping surface and an electromechanical coupling coefficient k. FIG. 3 is an explanatory diagram showing the relationship between the aspect ratio Le / T of the slipping surface and the elastic compliances S ₄₄ ^E and S ₃₃ ^E. 4 is a side view schematically showing the configuration of the piezoelectric sliding resonator. FIG. 5 is a ratio L / Le between the length L where the excitation electrodes facing each other overlap each other and the lateral dimension Le of the displacement strain surface. FIG. 6 is an explanatory view showing the relationship between the frequency displacement dF _OSC / F _OSC , and FIG. 6 shows the distance W between the opposing strain strain surfaces, that is, the ratio W between the width dimension W of the piezoelectric body and the vertical dimension T of the shear strain surface. It is explanatory drawing which shows the relationship between / T and the electromechanical coupling coefficient k.
[0014]
Reference numeral 1 in FIG. 1 denotes a piezoelectric sliding resonator, and the piezoelectric sliding resonator 1 includes a prismatic piezoelectric body 2 manufactured using a ceramic material such as LiTaO ₃ or LiNbO ₃ . . In the piezoelectric body 2, the width dimension is set to W, and the vertical dimension and the horizontal dimension of the displacement strain surface 2 a which is a rectangular side surface are set to T and Le, respectively. The piezoelectric body 2 is polarized along the axial direction (longitudinal direction), and an arrow P in FIG. 1 indicates the polarization direction.
[0015]
Furthermore, excitation electrodes 3 and 4 are respectively formed on the principal surfaces of the piezoelectric body 2 at this time, that is, on both principal surfaces that are orthogonal to the displacement strain surface 2 a and parallel to the displacement direction of the piezoelectric body 2. Has been. Therefore, when an AC voltage is applied through the excitation electrodes 3 and 4 opposed to each other, the piezoelectric body 2 vibrates in the thickness shear vibration mode and functions as the piezoelectric slip resonator 1.
[0016]
By the way, when the inventors of the present invention pay attention to the aspect ratio Le / T of the sliding surface 2a in the piezoelectric body 2 and examine the electromechanical coupling coefficient k of the piezoelectric sliding resonator 1, the sliding surface 2a. It has been found that there is a relationship as shown in FIG. 2 between the aspect ratio Le / T and the electromechanical coupling coefficient k. From the examination results shown in FIG. 2, the piezoelectric sliding resonator 1 corresponds to the change in the aspect ratio Le / T of the slipping sliding surface 2a regardless of whether the vibration wave number n is n = 1 to 4. It becomes clear that the electromechanical coupling coefficient k of the electromechanical coupling coefficient k changes periodically, and the electromechanical coupling coefficient k exhibits a maximum value corresponding to a specific aspect ratio Le / T.
[0017]
In FIG. 2, a schematic longitudinal sectional view showing a displacement distribution at each vibration wave number n of the piezoelectric sliding resonator 1 analyzed by using the finite element method is appended.
[0018]
That is, when the vibration wave number n is n = 1, the maximum value of the electromechanical coupling coefficient k, that is, k = 38% is obtained in the vicinity of the aspect ratio Le / T = 2.6. Therefore, the aspect ratio Le / T of the slip surface 2a of the piezoelectric body 2 is set in advance so that the electromechanical coupling coefficient k is close to the maximum value, and the vicinity of the maximum value of the electromechanical coupling coefficient k is set to the piezoelectric sliding resonator. 1 is used, the specific band of the piezoelectric sliding resonator 1 is increased. And when the specific band of the piezoelectric sliding resonator 1 is large, the variation in product quality can be reduced, and the improvement of the resonance characteristics can be realized.
[0019]
Further, paying attention to the material constant of the piezoelectric body 2 and examining the aspect ratio Le / T of the sliding surface 2a where the electromechanical coupling coefficient k has a maximum value, the relationship shown in FIG. 3 was found. That is, when the vibration wave number n is n = 1, the aspect ratio Le / T is Le / T = 0.72 · (S ₄₄ ^E / S ₃₃ ^E ) ^1/2 +1.41, and when n = 2. Le / T = 1.00 · (S ₄₄ ^E / S ₃₃ ^E ) ^1/2 +2.48 and the aspect ratio Le / T when the vibration wave number n is n = 3 is Le / T = 1. 26 · (S ₄₄ ^E / S ₃₃ ^E ) ^1/2 +3.59 Here, S ₄₄ ^E and S ₃₃ ^E are elastic compliances determined according to the material of the piezoelectric body 2.
[0020]
Then, according to the analysis of these relationships, the aspect ratio Le / T of the slippery sliding surface 2a at which the electromechanical coupling coefficient k becomes the maximum value is Le / T = α · (S ₄₄ ^E / S ₃₃ ^E ) It was found to be represented by ^1/2 + β. Here, the variable α is α = 0.27 · n + 0.45, the variable β is β = 1.09 · n + 0.31, and n is a positive integer. Further, since it has been experimentally revealed that a tolerance of about ± 0.3 is allowed for the aspect ratio Le / T of the slipping surface 2a, the deviation at which the electromechanical coupling coefficient k becomes a maximum value is apparent. The general formula of the aspect ratio Le / T of the slip surface 2a is Le / T = {α · (S ₄₄ ^E / S ₃₃ ^E ) ^1/2 + β} ± 0.3.
[0021]
That is, the aspect ratio Le / T of the slippery sliding surface 2a at which the electromechanical coupling coefficient k has a maximum value is determined in accordance with the elastic compliances S ₄₄ ^E and S ₃₃ ^E and the vibration wave number n. Therefore, if the aspect ratio Le / T of the slipping surface 2a thus determined is applied to the piezoelectric body 2, it becomes easy to use the vicinity of the maximum value of the electromechanical coupling coefficient k in the piezoelectric sliding resonator 1. As a result, the specific band of the piezoelectric sliding resonator 1 can be increased.
[0022]
Further, as shown in FIG. 4, paying attention to the overlapping length L of the excitation electrodes 3 and 4 formed on both main surfaces of the piezoelectric body 2 and facing each other, the deviation from the overlapping length L is noticed. When the change in the frequency displacement dF _OSC / F _OSC corresponding to the change in the ratio L / Le to the lateral dimension Le of the strain surface was examined, the relationship shown in FIG. 5 was found. According to the examination result shown in FIG. 5, the ratio L / Le between the length L of the excitation electrodes 3 and 4 that overlap each other and the lateral dimension Le of the displacement strain surface is 0.86 or more and 1 or less. That is, it is clear that the frequency displacement dF _OSC / F _OSC hardly changes within the range of 0.86 ≦ L / Le ≦ 1.
[0023]
Therefore, the ratio L / Le between the length L of the excitation electrode 3 on one side (upper side in the figure) and the excitation electrode 4 on the other side (lower side in the figure) facing each other and the lateral dimension Le of the displacement strain surface. Is within the range of 0.86 or more and 1 or less, even if the overlapping length L of the excitation electrodes 3 and 4 may change, the frequency change in the piezoelectric sliding resonator 1 can be small. . That is, when such a relationship is maintained, the frequency change of the piezoelectric sliding resonator 1 can be suppressed.
[0024]
Furthermore, the inventors of the present invention have the width W of the piezoelectric body 2 of the piezoelectric sliding resonator 1, that is, the distance W between the opposing strain strain surfaces 2 a and the displacement strain surface 2 a. Focusing on the ratio W / T with respect to the longitudinal dimension T and examining the electromechanical coupling coefficient k, it was found that there is a relationship as shown in FIG. That is, according to the examination result shown in FIG. 6, the ratio W / T between the interval W between the offset strain surfaces 2a facing each other and the vertical dimension T of the offset strain surface 2a is W / T ≦ 1.2, 1.3 ≦ W / T ≦ 1.5, 1.7 ≦ W / T ≦ 2.0, 2.2 ≦ W / T ≦ 2.5, 2.6 ≦ W / T ≦ 3.0 It can be seen that the electromechanical coupling coefficient k of the piezoelectric sliding resonator 1 increases as long as the relationship is expressed by any one of them.
[0025]
(Embodiment 2)
FIG. 7 is a perspective view showing a simplified configuration of the composite material vibration device according to Embodiment 2, and FIG. 8 is a perspective view showing a simplified configuration according to the modification. In addition, the code | symbol 11 in FIG. 7 shows the composite material vibration apparatus which concerns on Embodiment 2, and the code | symbol 12 in FIG. 8 has shown the composite material vibration apparatus which concerns on a modification.
[0026]
The composite material vibration device 11 according to the second embodiment is configured by using the piezoelectric sliding resonator 1 described in the first embodiment as a vibration member 13, and a prismatic vibration member 13 and its axial direction ( Reflecting layers 14 and 15 connected to both end faces along the longitudinal direction) and holding members 16 and 17 connected to outer end faces of these reflecting layers 14 and 15, respectively. The piezoelectric body 2 included in the vibration member 13 here is made of a ceramic material having a first acoustic impedance Z1 of about 3.4 × 10 ⁷ Kg / (m ² · s), for example. And polarized along the axial direction.
[0027]
The reflection layers 14 and 15 connected to the vibration member 13 have a second acoustic impedance Z2 lower than the first acoustic impedance Z1 of the vibration member 13, for example, 1.87 × 10 ⁶ Kg / (m Each is made of an epoxy resin having an acoustic impedance Z2 of about ² · s). Furthermore, the holding members 16 and 17 at this time are, for example, an acoustic impedance Z3 of about 3.4 × 10 ⁷ Kg / (m ² · s), that is, a third acoustic impedance higher than the second acoustic impedance Z2. Each is made from a ceramic material having Z3.
[0028]
Furthermore, on both main surfaces of the composite material vibration device 11 in which the holding members 16 and 17 are coupled to both ends along the axial direction of the vibration member 13 via the reflection layers 14 and 15, that is, piezoelectric. Excitation electrodes 18 and 19 are formed on both main surfaces which are orthogonal to the displacement strain surface 2a of the body 2 and parallel to the displacement direction of the piezoelectric body 2, respectively. In this case, the excitation electrode 18 on one side (upper side in the figure) includes a vibrating member 13 constituting the composite material vibration device 11 and a reflective layer connected to one side in the longitudinal direction (right side in the figure). 14 and the upper main surface of the holding member 16 are integrally formed.
[0029]
The excitation electrode 19 on the other side (lower side in the figure) is on the lower main surface of the vibrating member 13 and the reflection layer 15 and the holding member 17 connected to the other side in the longitudinal direction (left side in the figure). Are integrally formed. In FIG. 7, the excitation electrodes 18 and 19 are formed up to the outer end surfaces of the holding members 16 and 17, but these excitation electrodes 18 and 19 are formed up to the outer end surfaces of the holding members 16 and 17. Needless to say, it may be formed only on the main surface.
[0030]
In the composite material vibration device 11 configured as described above, when an AC voltage is applied via the excitation electrodes 18 and 19 facing each other with the piezoelectric body 2 included in the vibration member 13 interposed therebetween, the piezoelectric material of the vibration member 13 is piezoelectric. The body 2 vibrates in the thickness shear vibration mode. The vibration generated in the vibration member 13 propagates to the reflection layers 14 and 15, and the vibration propagated to the reflection layers 14 and 15 is reflected at the interfaces between the reflection layers 14 and 15 and the holding members 16 and 17. The For this reason, the propagation of vibration to the holding members 16 and 17 at this time is suppressed, and the holding members 16 and 17 do not cause displacement due to vibration. Thus, the composite material vibration device 11 can be reliably supported.
[0031]
By the way, in the composite material vibration device 11 according to the second embodiment, the reflection layers 14 and 15 are respectively connected to both end surfaces of the vibration member 13, and the holding members 16 and 17 are respectively connected to the reflection layers 14 and 15. It is connected. However, the present invention is not limited to such a configuration, and the reflective layer 14 is connected only to the end surface on one side (right side in the drawing) of the composite material vibration device 12 as shown in FIG. Further, the holding member 16 may be connected to the outer end surface of the reflective layer 14. In FIG. 8, parts and portions that are the same as those in FIG. 7 are denoted by the same reference numerals, and description thereof is omitted here.
[0032]
That is, even in the composite material vibration device 12 according to this modification, the vibration member 13 has the acoustic impedance Z1 and the reflection layer 14 has the second acoustic impedance Z2 lower than the first acoustic impedance Z1. On the other hand, the holding member 16 still has a third acoustic impedance Z3 higher than the second acoustic impedance Z2. Therefore, even in the composite material vibration device 12, the vibration generated in the vibration member 13 is reflected at the interface between the reflective layer 14 and the holding member 16, and the propagation of vibration to the holding member 16 is suppressed.
[0033]
【The invention's effect】
As described above, in the piezoelectric sliding resonator according to the first aspect of the present invention, the aspect ratio Le / T on the displacement strain surface of the piezoelectric body is set so that the displacement strain is set so that the electromechanical coupling coefficient k is in the vicinity of the maximum value. The aspect ratio Le / T of the surface is Le / T = {α · (S44E / S33E) 1/2 + β} ± 0.3 (where S44E and S33E are elastic compliance, α = 0.27 · n + 0.45, β = 1.09 · n + 0.31, where n is a positive integer). When the aspect ratio Le / T based on such a relationship is applied to the piezoelectric body, it becomes easy to use the vicinity of the maximum value of the electromechanical coupling coefficient k in the piezoelectric sliding resonator, and as a result, the piezoelectric sliding resonator. The ratio band can be increased. In addition, it is possible to reduce variations in product quality and improve resonance characteristics.
[0035]
In the piezoelectric sliding resonator according to the second aspect of the present invention, the ratio L / the length L between the excitation electrodes formed on the main surface of the piezoelectric body and facing each other and the lateral dimension Le of the displacement strain surface. Le is represented by 0.86 ≦ L / Le ≦ 1. As long as such a relationship exists, the frequency displacement dFOSC / FOSC hardly changes even when the overlapping length L of the excitation electrodes changes, so that the frequency change in the piezoelectric sliding resonator is suppressed. can do.
[0036]
In the piezoelectric sliding resonator according to the third aspect of the present invention, the ratio W / T between the gap W between the displacement strain surfaces and the vertical dimension T thereof is W / T ≦ 1.2 and 1.3 ≦ W / T ≦. 1.5, 1.7 ≦ W / T ≦ 2.0, 2.2 ≦ W / T ≦ 2.5, 2.6 ≦ W / T ≦ 3.0. With such a relationship, since the electromechanical coupling coefficient k of the piezoelectric sliding resonator is increased, it is possible to further increase the ratio band of the piezoelectric sliding resonator.
[0037]
According to a fourth aspect of the present invention, there is provided a composite material vibration device in which a reflection layer is connected to a vibration member made of a piezoelectric sliding resonator, and a holding member is connected to the reflection layer. Z2 is lower than the acoustic impedances Z1 and Z3 of the vibrating member and the holding member. Therefore, vibration that has propagated from the vibrating member to the reflective layer is reflected at the interface between the reflective layer and the holding member.
[0038]
That is, with the composite material vibration device configured as described above, the composite material vibration device can be supported using the holding member without affecting the vibration characteristics of the vibration member. Therefore, when compared with the energy confinement type, an excellent effect can be obtained that a reduction in size can be realized while increasing the ratio band.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a simplified configuration of a piezoelectric sliding resonator according to a first embodiment.
FIG. 2 is an explanatory diagram showing the relationship between the aspect ratio Le / T of the slipping surface and the electromechanical coupling coefficient k.
FIG. 3 is an explanatory diagram showing the relationship between the aspect ratio Le / T of the slipping slip surface and the elastic compliances S ₄₄ ^E and S ₃₃ ^E.
FIG. 4 is a side view showing a simplified configuration of a piezoelectric sliding resonator.
FIG. 5 is an explanatory diagram showing a relationship between a ratio L / Le between a length L where excitation electrodes facing each other overlap each other and a lateral dimension Le of a displacement strain surface and a frequency displacement dF _OSC / F _OSC .
FIG. 6 is an explanatory diagram showing a relationship between a ratio W / T between an interval W between opposing strain-straining surfaces and a longitudinal dimension T of the strain-straining surface and an electromechanical coupling coefficient k.
7 is a perspective view showing a simplified configuration of a composite material vibration device according to Embodiment 2. FIG.
FIG. 8 is a perspective view showing the modified example in a simplified manner.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric sliding resonator 2 Piezoelectric body 2a Displacement strain surface 3 Excitation electrode 4 Excitation electrode T Vertical dimension Le of the displacement strain surface 2a W Horizontal dimension W of the displacement strain surface 2a Width dimension of the piezoelectric body 2 (interval between the displacement strain surfaces 2a)
L Length of excitation electrodes 3 and 4 overlapping each other

Claims (4)

It has a prismatic piezoelectric body that excites the sliding vibration mode, and its rectangular displacement strain surface has a maximum electromechanical coupling factor k when its vertical dimension is T and its horizontal dimension is Le. The aspect ratio Le / T in the vicinity is
Le / T = {α · (S44E / S33E) 1/2 + β} ± 0.3
(However, S44E and S33E are elastic compliances, α = 0.27 · n + 0.45, β = 1.09 · n + 0.31, n is a positive integer)
A piezoelectric sliding resonator characterized by the following: Excitation electrodes are formed on both main surfaces orthogonal to the displacement strain surface and parallel to the displacement direction of the piezoelectric body, and the length L and the excitation electrodes facing each other overlap each other. The ratio L / Le to the lateral dimension Le of the shear plane is
0.86 ≦ L / Le ≦ 1
The piezoelectric sliding resonator according to claim 1, wherein: The ratio W / T between the gap W between the offset strain surfaces facing each other and the vertical dimension T of the offset strain surfaces is:
(1) W / T ≦ 1.2
(2) 1.3 ≦ W / T ≦ 1.5
(3) 1.7 ≦ W / T ≦ 2.0
(4) 2.2 ≦ W / T ≦ 2.5
(5) 2.6 ≦ W / T ≦ 3.0
3. The piezoelectric sliding resonator according to claim 1, wherein the piezoelectric sliding resonator is represented by any one of the above. A composite material vibration device using the piezoelectric sliding resonator according to any one of claims 1 to 3 as a vibration member,
A vibration member having an acoustic impedance of Z1, a second acoustic impedance Z2 lower than the first acoustic impedance Z1, a reflective layer coupled to the vibration member, and a second acoustic impedance higher than the second acoustic impedance Z2. And a holding member connected to the reflecting layer, and reflects the vibration propagated from the vibrating member to the reflecting layer at the interface between the reflecting layer and the holding member. A composite material vibration device having a structure.

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