JPH0475719B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a bolted lunge transducer used in an underwater ultrasonic transducer,
The purpose is to reduce the size and weight of a bolt-tight lunge resonator and at the same time increase its power. Conventionally, a bolt-tight lunge resonator includes a front mass 11 made of a highly rigid material such as aluminum alloy, titanium alloy, or steel, and a ring-shaped piezoelectric element disposed between the front mass 11 and the rear mass 13, as shown in FIG. Ceramics 12, rear mass 13 made of a highly rigid material such as stainless steel like the front mass, and ring-shaped piezoelectric ceramics 12.
The bolt 14 and nut 15 are made of a high tensile strength alloy such as Cr-Mo steel, which has the function of applying compressive stress to the steel, and has the great feature of being capable of high-power driving. Here, the ring-shaped piezoelectric ceramic 12 uses a longitudinal effect longitudinal vibration mode (33rd mode) which provides a much larger electromechanical coupling coefficient than a transverse effect longitudinal vibration mode (31st mode). Adjacent ring-shaped piezoelectric ceramics are polarized in opposite directions as shown by the arrows in the figure, and are electrically connected in parallel to achieve matching with the power amplifier. In addition, since ceramics are generally weaker against tensile stress than compressive stress, a static bias compressive stress is applied in advance by bolts 14 and nuts 15, and the structure is strong enough to withstand use even under high power conditions. It's summery. As is well known, in a bolt-fastened lunge resonator having such a structure, a half wavelength resonance mode is used, and there is a vibration node in the piezoelectric ceramic 12, and the stress is applied to the piezoelectric ceramic 12 and the bolt 14.
It works in a concentrated manner. The bolt-fastened lunge transducers used in the above-mentioned underwater ultrasonic transducer are usually arranged in large numbers in order to obtain the desired directivity, and such a large number of transducer arrays are inevitably Because it is large and extremely heavy,
Recently, there has been a strong demand for smaller and lighter bolt-tight lunge resonators. However, until now, a vibrator shape that is compatible with both size and weight reduction and high power generation has not been obtained. In particular, bolt-tight lunge transducers used in sonar systems for ships are arrayed in large numbers in order to obtain the desired directivity in a limited space, and it is necessary not only to reduce the weight but also to shorten the transducer length. be. The present invention was made in order to achieve high power while reducing the size and weight of a bolt-tight lunge resonator. This is what we provide. That is, in the present invention, in a half-wavelength resonant bolted lunge van oscillator consisting of a front mass part, a piezoelectric ceramic part, and a rear mass part, the acoustic radiation cross-sectional area of the front mass part is S ₁ and the cross-sectional area of the piezoelectric ceramic part is S 1 . _2. The cross-sectional area of the bolt part is _S3 , the cross-sectional area of the rear mass part is S4, the length of the front mass part is _l1 , and the length from the acoustic radiation end of the front mass part to the vibration node is _l0 . When the cross-sectional area of the piezoelectric ceramic part is _S2 , the cross-sectional area of the bolt part is _S3.
is set quite small, and 0.03 for the first half from the acoustic radiation end of the front mass section to the vibration node.
S ₂ /S ₁ 0.25, 0.1<l ₁ /l ₀ 0.35, S ₂ /S ₄ 0.15 for the rear half from the vibration node to the rear mass end
This is a bolt-tight lunge van oscillator characterized by the following. The present invention will be explained in detail below. In order to obtain a bolt-fastened Lange-Van vibrator having an optimal shape, which is the objective of the present invention, the first half wavelength section from the front mass to the vibration node and the second half wavelength section from the vibration node to the rear mass are considered. . First, we will consider the mechanical system of a bolt-tight Languevan oscillator using an equivalent composite transmission line, and here we will discuss the standardized oscillator length, which is a guide for miniaturization, and the standardized oscillator mass, which is a guide for weight reduction. Considering the stress applied to the bolts and piezoelectric ceramic parts when operated underwater, we will reveal a vibrator shape that is both smaller and lighter and has excellent mechanical strength at high power.
Furthermore, we conducted an analysis that included the electrical system to find the relationship between the capacitance ratio, which is closely related to electromechanical conversion efficiency (the smaller the capacitance ratio, the higher the energy conversion efficiency) and the resonator shape, and finally analyzed the mechanical and electrical systems. Taking both into consideration, we found the optimal transducer shape that reduces weight and increases power at the same time. In order to obtain a small, lightweight, and high-power vibrator, we first conduct a theoretical study on the half section of the vibrator from the acoustic radiation end to the vibration node, as shown in Figure 2. In Fig. 2, part 11 is the front mass part, part 12 is the piezoelectric ceramic part, part 14 is the bolt part, _l1 is the length of the front mass, and _l2 is the length of the piezoelectric ceramic part (= length of the bolt part). , l ₀ (=l ₁ +l ₂ ) indicates an effective quarter wavelength. FIG. 3 shows an equivalent composite transmission line for the half-section model shown in FIG. 2. In Fig. 3, the density of the part (=1, 2, 3) is ρ _i , the longitudinal wave velocity is c _i , the cross-sectional area is S _i , and the phase constant is β _i (=ω/c _i , ω;
Angular frequency, ω = 2πf), characteristic impedance density
z _pi (=ρ _i c _i ), characteristic impedance Z _pi (=z _pi Si)
and R _a is the acoustic radiation impedance, which is expressed by the following equation. Ra＝ρ ₀ c ₀ S ₁ (1) where ρ ₀ ; density of water c ₀ ; speed of sound of water S ₁ ; radiation cross section However, the effective longitudinal wave velocity for the piezoelectric ceramic part is c _2e (=√1 ₂ ^E ₃₃ , s ^E ₃₃ : elastic compliance when electric field is constant), and the effective phase constant, characteristic impedance density, and characteristic impedance are β _2e , Z _02e , and Z _02e , respectively. The resonance equation of the equivalent composite transmission line shown in FIG. 3 can be obtained by setting the sum of the impedances of the respective transmission lines as seen from 1-1' to the left and right to zero. (Since it is the resonant frequency of the vibrator itself, R _a =0) That is, Z ₀₁ tan (β ₁ l ₁ ) − Z _02e cot (β _2e l ₂ ) −Z ₀₃ cotβ ₃ l ₂ =0 (2) Here, as the ratio of characteristic impedance, K _12e = Z _02e /Z ₀₁ (3) K ₁₃ = Z ₀₃ /Z ₀₁ (4) Also, the reference constant α ₁ ,
Introducing α ₂ , β ₁ l ₁ =ωl ₁ /C ₁ =π/2α ₁ (5) β _2e l ₂ =ωl ₂ /c _2e =π/2α ₂ (6) β ₃ l ₃ =ωl ₂ /c ₃ =π/2(C _2e /c ₃ ) α ₂ (7) Then, equation (2) becomes as follows. tanπ/2α ₁ −K _12e cotπ/2α ₂ −K ₁₃ cotπ
/2(C _2e /c ₃ )α ₂ =0(8) Determine the material of each part of the vibrator, and then calculate the cross-sectional area ratio S ₂ /
When S ₁ and S ₃ /S ₁ are given, equation (8) becomes an equation consisting of two variables α ₁ and α ₂ . That is, when α ₁ is given, α ₂ corresponding to α ₁ is found, and the relationship between the size ratio l ₁ /l ₂ and the resonant frequency is found. The total mass M of the half-section oscillator shown in FIG. 2 is given by M=ρ ₁ l ₁ S ₁ +ρ ₂ l ₂ S ₂ +ρ ₃ l ₃ S ₃ (9). Since the resonant frequency and length are inversely proportional to each other, the optimum shape for weight reduction per unit acoustic radiation area standardized by the resonant frequency is given by Mfr/S ₁ . Further, if this is normalized by the characteristic acoustic impedance density z ₀₂ (=ρ ₂ c _2e ) of the piezoelectric ceramic part, the normalized resonator mass M _o is M _o =Mf _r /z _02e S ₁ = (Z ₀₁ / z _02e ) {α ₁ /4
+K _12e α ₂ /4 + K ₁₃ (c _2e /c ₃ ) α ₂ /4}(10). Next, l ₀ (=l ₁ +l ₂ ) is an effective quarter wavelength, and l ₀ is inversely proportional to the resonant frequency _fr . That is, f _r l ₀ is a guideline for minimizing the vibrator length, but normalization is performed using the sound speed of piezoelectric ceramic c _2e . The normalized resonator length L _o , which is a guideline for miniaturization, is given by Ln=f _r /C _2e l ₀ =α ₁ /4 (C ₁ /C _2e )+α ₂ /4 (11). This is because not only M _o but also L _o is considered here, but a vibrator shape that reduces M _o and a vibrator shape that reduces L _o do not necessarily match. Prior to the calculation, Table 1 shows the density and longitudinal wave velocity of the materials normally used for each part of the bolt-tight LangueVan transducer.

[Table] Using the materials shown in Table 1, as an example, the ratio of the bolt cross-sectional area to the acoustic radiation area S ₃ /S ₁ =
Assuming that 0.006 is constant, when the piezoelectric ceramic cross-sectional area S ₂ /S ₁ with respect to the acoustic radiation area is used as a parameter,
FIG. 4 shows the relationship between the ratio l ₁ /l ₀ of the length of the front mass to the effective quarter wavelength and the normalized total mass M _o of the front half of the oscillator. From Figure 4, l ₁ /l ₀
When is in the range of 0 to 0.4, M _o increases slowly as l ₁ /l ₀ increases, but when l ₁ /l ₀ exceeds 0.4, M _o increases rapidly, and the oscillator It can be seen that in order to reduce the weight of , S ₂ /S ₁ and l ₁ /l ₀ should be made smaller. Incidentally, the cross-sectional area _S3 of the bolt is usually designed to be much smaller than the cross-sectional area _S2 of the piezoelectric ceramic portion, as shown in FIG. This is because the electromechanical conversion efficiency decreases as S ₃ approaches S ₂ .
In the range where S ₃ is much smaller than S ₂ , M _o is S ₃ /S ₁
is hardly affected by. At this time, if the cross-sectional areas S ₂ and S ₃ of the piezoelectric ceramic part and the bolt part are set smaller than the acoustic radiation area S ₁ , the weight can be reduced accordingly, but stress will be concentrated in the bolt part and the piezoelectric ceramic part. Therefore, it can be inferred that it is difficult to reduce the weight in consideration of high power by simply reducing the cross-sectional areas S ₂ and S ₃ . Next, as in Fig. 4, the cross-sectional area ratio S ₃ /S ₁ = 0.006
FIG. 5 shows the relationship between l ₁ /l ₀ and the normalized resonator length L _o when the cross-sectional area ratio S ₂ /S ₁ is set as a parameter. From Fig. 5, it is more advantageous to reduce the size of the cross-sectional area ratio for the same l ₁ /l ₀ .
Furthermore, it can be seen that L _o is minimized when l ₁ /l ₀ is set to 0.3 to 0.5. Next, we will theoretically examine the vibration stress applied to the piezoelectric ceramic part and the bolt part of the bolted lunge van oscillator. Normally, when transmitting waves underwater, the stress acting inside the vibrator is different from the state of vibration in the air, and a reaction due to the acoustic radiation impedance of the water is further added to the acoustic radiation end face. Here, when the acoustic radiation surface is resonated at a unit speed (1 m/sec) under water load, the stress applied to the piezoelectric ceramic part and the bolt part is determined from the equivalent circuit shown in Figure 3, and the oscillator of these stresses is calculated. Calculate shape dependence. Concerning the stress in the piezoelectric ceramic part, the part receiving the maximum stress is the vibration node shown in FIG. 32-2', and the stress there is designated as T _pn . Dimensional ratio when S ₂ /S ₁ is used as a parameter when S ₃ /S ₁ = 0.006 constant as in Figure 4
The relationship between |T _pn | and l ₁ /l ₀ is shown in FIG.
The smaller S ₂ /S ₁ , the larger l ₁ /l ₀ |T _pn |
It can be seen that is increasing. Next, in exactly the same manner, the relationship between the stress acting on the bolt portion and the shape of the vibrator is determined. The vibration stress acting on the bolt at the joint with the front mass is T _bc , and the vibration stress acting on the bolt at the vibration node is T _bn . ｜T _bc ｜, ｜T _bn ｜
Figure 7 shows the relationship between the
As shown in the figure. In FIG. 7, the solid line indicates the characteristic of |T _bc |, and the dotted line indicates the characteristic of |T _bn |. For l ₁ /l ₀ > 0.2, |T _bc |
There is not much difference between and |T _bn |, but |T _bc |<|
T _bn | and as l ₁ /l ₀ increases |T _bc |,
|T _bn | also increases, and at the same time, |T _bc | and |T _bn | approach each other. However, when l ₁ /l ₀ <0.1, l ₁ /l ₀ decreases,
In other words, as the length of the front mass becomes shorter, |
When T _bc |, |T _bn | increases, the following behavior occurs. This is because when the front mass becomes extremely thin, stress is concentrated at the joint between the bolt and the front mass due to the reaction of the acoustic radiation impedance of water. The parts with the weakest mechanical strength in a bolted lunge resonator are the joint between the front mass and the bolt and the ceramic center part. In order to reduce the size and weight of the vibrator and to increase its power at the same time, it is desirable to have a vibrator shape that prevents stress from concentrating on a portion with weak mechanical strength for a constant vibration velocity at the acoustic radiation end. In order to reduce the size and weight of a vibrator, it is necessary to consider not only the vibrator mass but also the vibrator length. Regarding mechanical vibration systems, Figure of Merit FMM _n for weight reduction and Figure of Merit for miniaturization
Merit FMM _l is given as follows. Equation (12) is closely related to the maximum acoustic power that can be extracted per unit mass of the resonator, and the larger the FMM _n , the better the shape of the resonator for weight reduction.On the other hand, equation (13) is There is a close relationship with the maximum acoustic power that can be extracted per unit length, and FMM _l
The larger the value, the better the resonator shape for miniaturization. Therefore, a new Figure of Merit that takes into account both the miniaturization and weight reduction of the resonator.
FMM _nl is given by the geometric mean of FMM _n and FMM _l . becomes. The larger the value of FMM _nl , the more compact and lightweight the resonator shape is. Next, the capacity ratio γ, which is a guideline for electromechanical conversion efficiency, is
The equivalent transmission line of the piezoelectric ceramic part shown in Fig. 3 is transformed into Martin's equivalent circuit (GEMartin:
“Vibrations of Coaxially Segmented,
Longitudinally Polarized Ferroelectric
Tubes”, Journal of Acoust.Soc. Am. Vol. 36, No. 8, pp. 1496-1506, (1964)), it can be easily obtained from the relationship between the resonance and anti-resonance frequencies. The smaller γ is, the more Since the electromechanical conversion rate is excellent, the Figure of Merit FM _nl for reducing the size and weight of the oscillator including the electrical system of the 1/4 wavelength portion from the acoustic radiation end is expressed by the following equation. FM _nl = FMM _nl / γ (15) Using the materials shown in Table 1 as the materials for each part of the vibrator, calculate the electromechanical coupling coefficient of piezoelectric ceramics.
Figure 8 shows the FM _n characteristics when k ₃₃ =0.50.
When the front mass becomes thinner and l ₁ / l ₀ becomes less than 0.1, the front mass itself undergoes bending vibration during sound radiation, and the sound radiation surface of the front mass is no longer able to make piston movement, resulting in a decrease in sound radiation efficiency. This is well known. So, first
A range in which l ₁ /l ₀ is greater than 0.1 is suitable for practical use. _S2 /
As S ₁ becomes smaller and becomes less than 0.03, it becomes less
Although FMM _nl does not increase, the capacity ratio γ increases, and as a result, FM _nl decreases. Furthermore, S ₂ /S ₁
If the cross-sectional area of the piezoelectric ceramic part becomes smaller than <0.03, the wall thickness of the piezoelectric ceramic part becomes thinner, and the radial strength of the piezoelectric ceramic ring cannot be increased against the static stress when the bolt is tightened, which is preferable in practice. do not have. Furthermore, as S ₂ /S ₁ increases, Lo _{and Mo} increase, so FM _nl decreases. The practically required value of FM _nl is 6 when k ₃₃ = 0.50.
×10 ^-8 m ² /N. However, this is not satisfied with conventional vibrator shapes. Although not shown in Figure 7, we calculated the FM _nl for the vibrator shape in more detail and found that l ₁ /l ₀ >0.35, S ₂ /S ₁
>0.25, it was found that the value of FM _nl does not exceed 6×10 ⁻⁸ m ² /N. In other words, a vibrator shape that increases FM _nl , in other words, a vibrator shape that is small, lightweight, and capable of high power, has a cross-sectional area of 0.03S ₂ /S ₁ 0.25 and a length of 0.1l ₁ /l _0.
It is found to be 0.35. Next, when using carbon fiber reinforced resin (C-FRP) as a front mass material, which has recently attracted attention as an advanced composite material that has a rigidity comparable to or higher than that of Al alloys and a density lower than that of Al alloys. Figure 9 shows the FM _n characteristics of . From Figure 9,
The maximum value of FM _n value when the Al alloy shown in Fig. 8 is used for the front mass almost matches that of C-FRP, but the maximum value of FM _n is slightly smaller than l ₁ ~
l ₀ is shifted to the larger side. However, it is clear that the tendency of the vibrator shape to increase FM _n is exactly the same even though the front mass materials are different. Next, we will discuss the shape of the oscillator, which can be made smaller and lighter and at the same time has higher power, regarding the quarter-wavelength portion in the latter half from the vibration node to the rear mass.
FIG. 10 shows a physical model of the half-section of the bolted lunge van oscillator shown in FIG. 1 from the vibration node to the rear mass. 1 in Figure 10
2' and 14' are a piezoelectric ceramic part and a bolt part, respectively, and 13 is a rear mass part. l′ ₀ is the effective quarter wavelength, l′ ₂ is the piezoelectric ceramic part (=
(bolt part) length, _l4 is the length of the rear mass part. 12 and 14' are mechanically continuous with the piezoelectric ceramic part and bolt part 14 from the front mass to the vibration node shown in FIG.
It is assumed that the material of 2' and the material of 14 and 14' are the same, and the cross-sectional areas of the portions 12 and 12' are the same. Here, in order to find the optimal shape of the vibrator, the vibrator is divided into two halves, the front half and the back half, but in reality, 12 and 12', and 14 and 14' are integrated. When the acoustic radiating end of the front mass vibrates at a certain speed, the vibration contacts in the front and rear halves of the transducer are common, and the stress acting thereon is, of course, equal. At this vibration node, the maximum stress occurs unless the length of the front mass becomes extremely short. The vibration stresses T _pn and T _bn in this part have already been determined. Assume that the density of 13 parts is ρ ₄ , the speed of sound is c ₄ , and the cross-sectional area is S ₄ . _{The characteristic} acoustic impedance _{Z 04} and phase constant β _{4 are} Z ₀₄ = ρ ₄ c ₄ S ₄ = z ₀₄ S _{4 (} 16) ) becomes. Total capacity of the second half of the transducer shown in Figure 10
Let it be M′. Regarding the mass of the vibrator in the rear half, the resonant frequency and length are inversely proportional to each other, and since the cross-sectional shapes of the piezoelectric ceramic part are the same in the front and rear halves, the characteristic acoustic impedance of the piezoelectric ceramic part Z _02e Can be standardized.
If the normalized total mass is M′ _o , then M′ _o is M′ _o = M′f _r /Z _02e = 1/K _42e {α ₄ /4 + K _4
2e α′ ₂ /4+K ₄₃ (c _2e /c ₃ )α′ ₂ }(18) However, π/2α′ ₂ = β _2e l′ ₂ (19) K _42e =Z _02e /Z ₀₄ (20) K ₄₃ =Z ₀₃ /Z ₀₄ (21). Since the stress at the vibration node is determined by the first half of the oscillator, the smaller the normalized mass M′ _o and the smaller the capacitance ratio γ′ of the second half of the oscillator, the lower the figure.
Of Merit is superior. in the second half
Figure of Merit FM′ _nl is given by the following equation. Here, L′ _o is the normalized oscillator length for the second half of the oscillator, L′ _o = f _r /c _2e l′ ₀ = α′ ₂ /4 + α ₄ /4 (c ₄ /c _2e )
It is given by (23). Al alloy as rear mass material,
Stainless steel (ρ=7.91×10 ³ Kg/m ³ , C
Figures 11 and 12 show the dependence of _FM'nl on the shape of the oscillator when using the oscillator shape (=5.00×10 ³ Kg/sec), respectively. In both cases, as S ₂ /S ₄ increases, FM′ _nl
increases, and when S ₂ /S ₄ becomes 0.15 or more, it tends to be saturated, and the shape of the oscillator for increasing FM′ _nl tends to be exactly the same. Furthermore, when comparing Al alloy and stainless steel, it is clear that stainless steel with a higher density is more advantageous in increasing FM' _nl because L' _o can be made smaller. A value of FM′ _nl of 1.1 or more is desired, but if a material with low density such as an Al alloy is used as the rear mass material,
It is difficult to achieve FM′ _nl >1.1. FM′ _nl
To achieve >1.1, from Figure 12, S ₂ /S ₄
Must be 0.15. If l ₄ /l′ ₀ <0.1, the mechanical strength of the rear mass becomes weak, and the rear mass itself becomes extremely susceptible to deflection, especially at high power, which is not preferable since it becomes difficult to maintain a large power linearity. Also, when S ₂ /S ₄ becomes 0.70 or more, bolt 14 and nut 1 as shown in Fig.
5 becomes difficult and impractical. Needless to say, FM′ _nl can be further increased by using a material such as Mo or W, which has a higher density than stainless steel, for the rear mass. Above is the theoretically considered Figure of Merit.
Regarding FM _nl and FM′ _nl , the larger FM _{nl is} , the better the electroacoustic conversion efficiency is, and if the vibration stress applied to the piezoelectric ceramic and bolt part is the same, the vibration velocity of the acoustic radiation end face per transducer mass x transducer length. v can be increased. The vibration velocity v is proportional to the square root of the acoustic radiation energy Pa. Also, FM′ _nl
The larger is, the better the electroacoustic conversion efficiency is, and the smaller and lighter the vibrator can be realized. That is, if the acoustic radiation cross section S ₁ and the resonant frequency f _r are the same, then
FM _nl , FM′ _nl is larger, Figure of Merit However, Mt: Total mass of the resonator Lt: Length of the resonator can be increased. Next, as an embodiment of the present invention, A, B, C, and D4 having different shapes as shown in Table 2 have a resonance frequency in the 10KHz band and have the same acoustic radiation area _S1 .
We prototyped a bolt-on Lange-Vant transducer for various types of underwater ultrasonic transducers and evaluated its figure of merit. Note that all of the vibrators A, B, C, and D have k ₃₃ =0.50 as piezoelectric ceramics.
NEPEC-1, Al alloy as front mass material,
Stainless steel is used as the rear mass material, and _Cr - _Mp steel is used as the bolt/nut material. In recent years, the sounding distance of sonar systems has increased,
In parallel with this, vibrators are also required to be smaller, lighter, and more powerful. Specifically, regarding the 10KHz band vibrator, the FM value is 150 (W/Kg・m) ^1/2
The above is required.

[Table] The values of FM _nl and FM′ _nl calculated from the four shapes of vibrators A, B, C, and D shown in Table 2 are
The plots are shown in FIG. figure of
Regarding the experimental evaluation of Merit, we experimentally drove the vibrator, determined the relationship between the acoustic output power and the electrical input power, and calculated the acoustic output power (Pa) when the linearity of the acoustic output power with respect to the electrical input power suddenly deteriorated. Then, calculate FM according to equation (24). Oscillator A satisfies FM′ _nl > 1.1, but FM _nl > 6×
10 ^-8 m ² /N is not satisfied. Transducer B is FM _nl
>6×10 ^-8 m ² /N and FM′ _nl >1.1 are both just barely satisfied. Oscillator C has FM _nl > 6
×10 ⁻⁸ N/m ² and FM′ _nl >1.1 are both not satisfied. Also, the transducer D has FM _nl >6×10 ^-8 N/m ²
and FM′ _nl >1.1 are both satisfied with a comfortable margin. The results are shown in Table 3.

[Table] It is clear that the larger the values of FM _nl and FM′ _nl shown in FIGS. 8 and 12 are, the more a vibrator that is actually smaller and lighter and has a larger output sound pressure can be obtained. In particular, it can be seen that the vibrator D with large values of both FM' _nl and FM' _nl is small and lightweight and has excellent high power characteristics. As described in detail above, according to the present invention, a bolted lunge transducer for an underwater ultrasonic transducer that is small and lightweight and has excellent high power characteristics can be obtained, and has great industrial value.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a bolted lunge transducer used in an underwater ultrasound transducer, Figure 2 is a model diagram of the first half of the transducer from the acoustic radiation end to the vibration node, and Figure 3 is the same as that of Figure 2. equivalent circuit diagram,
Figure 4 shows the relationship between the normalized mass M _o of the front half of the vibrator and the shape of the vibrator, and Figure 5 shows the relationship between the normalized length L _o of the front half of the vibrator and the shape of the vibrator. Figure 6 shows the relationship between the stress T _pn at the vibration node of the piezoelectric ceramic part and the shape of the vibrator. Figure 7 shows the stress T _bc acting on the bolt at the joint with the front mass and the bolt part. Diagram showing the relationship between the stress T _bn acting on the vibration nodes of and the vibrator shape, No. 8
The figure shows the relationship between Figure of Merit FM _nl and the shape of the vibrator to reduce the size and weight of the front half of the vibrator, including the electric system. Figure 9 shows the relationship between the shape of the vibrator and the front mass material.
A diagram showing the relationship between FM _nl and the vibrator shape when using FRP, Figure 10 is a physical model diagram of the half section of the vibrator from the vibration node to the rear mass end of the bolted lunge van oscillator, Figure 11, Figure 12 shows the rear half of the vibrator when Al and stainless steel are used as the rear mass materials, respectively.
Merit FM′ _nl characteristic diagram is shown. In the figure, 11 is the front mass, 12, 1
2' is a piezoelectric ceramic ring, 13 is a rear mass,
14 and 14' are bolts, 15 is a nut, _l1 is the length of the front mass, _l2 , l' ₂ is the length of the piezoelectric ceramic part, _l4 is the length of the rear mass, _l0 , l' ₀ are the effective 4
1/1 wavelength, S ₁ is the cross-sectional area of the front mass, S ₄ is the cross-sectional area of the rear mass, k ₃₃ is the electromechanical coupling coefficient, R _a is the acoustic radiation impedance, Z ₀₁ , Z _02e , Z ₀₃ are the characteristic acoustic impedances, β ₁ , β _2e and β ₃ are phase constants.

Claims (1)

[Claims] 1. In a half-wavelength resonant bolt-tight Languevan vibrator consisting of a front mass part, a piezoelectric ceramic part, and a rear mass part, the acoustic radiation cross-sectional area of the front mass part is S ₁ , and the cross-sectional area of the piezoelectric ceramic part is S 1 .
S ₂ , the cross-sectional area of the bolt part is S ₃ , the cross-sectional area of the rear mass part is S ₄ , the length of the front mass part is l ₁ , and the length from the acoustic radiation end of the front mass part to the vibration node is l ₀ When, the cross-sectional area of the piezoelectric ceramic part S ₂
The cross-sectional area S ₃ of the bolt part is set quite small compared to that, and for the first half from the acoustic radiation end of the front mass part to the vibration node, 0.03S ₂ /S ₁ 0.25, 0.1
<l ₁ /l ₀ 0.35, and S ₂ /S ₄ 0.15 for the rear half from the vibration node to the end of the rear mass.