JPH0463347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a transducer for an ultrasonic distance meter that transmits and receives ultrasonic waves in the air.

More specifically, the present invention relates to improving the characteristics of a transducer for an ultrasonic distance meter.

(Prior Art) FIG. 11 is a diagram illustrating the configuration of a conventional example that has been commonly used.

In the figure, 1a is a cylindrical piezoelectric vibrator made of ceramics. 2a is a plastic case that also serves as an acoustic matching layer. 3a
is a damping material for damping the piezoelectric vibrator 1a. Reference numeral 4a denotes a reflecting umbrella for changing the direction of ultrasonic waves transmitted and received by the piezoelectric vibrator 1a to provide directivity.

In the above configuration, (1) When transmitting ultrasonic waves When an electric pulse is applied to the piezoelectric vibrator 1a, the piezoelectric vibrator 1a causes breathing vibration in the radial direction and is directed into the air in the normal direction of the outer periphery. It generates supersonic pressure. This ultrasonic wave is changed in its traveling direction by the reflector 4a, becomes a donut-shaped beam as shown in FIG. 12, and travels downward in FIG. 11.

(2) In the case of receiving ultrasonic waves The ultrasonic waves incident from below in FIG. 11 are converged by the reflecting umbrella 4a, pass through the case 2a, and apply stress to the outer circumference of the piezoelectric vibrator 1a. The piezoelectric vibrator 1a generates an electric field between electrodes in response to applied stress.

(Problems to be Solved by the Invention) Specific applications of ultrasonic transceivers based on such a principle include distance meters and level meters. In such a device, the following characteristics are required.

(1) High damping characteristics An ultrasonic distance meter is an instrument that determines the distance L to an object by emitting ultrasonic waves toward the object and measuring the time t it takes for the ultrasonic wave to be reflected and returned. Here, L=1/2ct (1) c: Speed of sound in the propagation medium However, the ceramic piezoelectric vibrator 1a is
Generally, it has a large inertia, so even after the electric drive pulse a shown in FIG. 13A disappears, the 13th
As shown in Figure B, the damping vibration b continues, which is referred to as residual vibration b.If the distance to the measurement object is short, the residual vibration b continues as shown in Figure 13C. While the light remains, the reflected wave c may arrive, making it impossible to separate and distinguish between the two. That is, it becomes difficult to measure at close range.

Conversely, when the distance to the measurement target is long, the reflected wave amplitude becomes extremely small, as shown in FIG. 13D, and it becomes necessary to electrically amplify the received voltage to a large extent. At this time, the electromotive force caused by the residual vibration b is also amplified, so in order to avoid mistakenly detecting the residual vibration b, until the amplitude of the residual vibration b becomes smaller than the amplitude of the reflected wave c,
The detection prohibited area (dead zone) e of the reflected wave c is determined by the thirteenth
It is necessary to provide it as shown in Figure E.

From the above, if you want to measure long distances,
On the other hand, making it possible to measure short distances (shortening the dead zone) makes it impossible to measure short distances.
A problem arises in that it becomes difficult to measure long distances where reflection is small.

In order to avoid this situation, the piezoelectric vibrator 1a is generally damped by a damping material 3a shown in FIG.
However, this method has the following two problems.

It is extremely difficult to select a damping material that has a satisfactory or appropriate damping effect over a wide temperature range. That is, since the physical properties of many viscous substances change greatly depending on temperature, in reality, it is difficult to find a damping material that provides necessary and sufficient damping characteristics from low to high temperatures.

Applying damping with a damping material means suppressing vibration, which leads to a reduction in the sound pressure generated during transmission.

(2) Highly efficient transmission and reception characteristics It is desirable to be able to transmit and receive sound with low power from the standpoint of energy conservation and safety.

However, the transducer shown in the conventional example in FIG. 11 has the following two problems.

Since damping is applied by the damping material 3a, in order to obtain the desired vibration amplitude of the vibrator, it is necessary to apply considerably larger driving power, for example, 10 times that of the piezoelectric vibrator 1a alone, or approximately 1 kV when expressed in voltage. be.

Acoustic impedance (ρc:
ρ: density, c: sound speed) is about five orders of magnitude larger than the acoustic impedance of air, so even if the piezoelectric vibrator 1a vibrates, the energy transmitted to the air is extremely small. In order to improve this, sound is emitted into the air through a case 2a made of plastic which is acoustically softer (having a smaller acoustic impedance ρc) than the piezoelectric vibrator 1a as an acoustic matching layer. Furthermore, the energy propagation efficiency is maximized when the thickness of the plastic layer 2a is 1/4 wavelength.
However, if the sound speed in plastic changes due to temperature changes, the equivalent plastic layer thickness will decrease by 1/1.
This results in a deviation from the four wavelengths, and the sound propagation efficiency deteriorates. In the end, the existence of the matching layer 2a
This appears as a temperature change in the transmission and reception characteristics.

(2) Simple structure As mentioned above, the conventional transducer shown in Fig. 11 has the following characteristics in order to bring its characteristics closer to ideal ones:
In addition to the piezoelectric vibrator 1a, additional elements such as a damping material 3a and an acoustic matching layer 2a are required, and as a result, the characteristics are significantly affected by temperature changes etc. ing.

Ideally, these extra elements would not be present.

The present invention solves these problems.

An object of the present invention is to provide an ultrasonic transducer that has a simple structure, high damping characteristics, good efficiency, robustness, and high reliability.

(Means for solving the problem) In order to achieve this object, the present invention includes a cylindrical holder, and a cylindrical holder, which is separated from each other in the axial direction of the holder, and each of which is arranged on the circumferential surface of the holder. at least two or more recesses provided in a ring shape over the entire circumferential circumference of the holder, and a peripheral surface of the holder other than the portion where the recesses are formed and provided to cover the outer peripheral surface of the holder. A cylindrical polymer piezoelectric film whose contacting part is fixed and whose part facing the recess forms a ring-shaped chamber with the recess, and an electrode plate provided on the outer and inner peripheral surfaces of the polymer piezoelectric film, respectively. a conical reflector whose head side is attached to one end of the holder and which imparts directivity in the axial direction of the holder to the transmitted and received ultrasonic waves; and a conical reflector which is provided on the holder and has one end opening into the chamber. A transducer for an ultrasonic rangefinder was constructed which included a pressure equalizing hole whose other end opened to the outside.

(Function) In the above configuration, when an electric pulse is applied to the polymer piezoelectric film, the polymer piezoelectric film causes respiratory vibration in the radial direction. The ultrasonic waves generated by this respiratory vibration have their traveling direction changed by a reflecting umbrella, and travel as a donut-shaped beam.

On the other hand, if pressure is applied to the polymer piezoelectric membrane from the outside, the polymer piezoelectric membrane 1 will expand and contract, generating a voltage between the electrodes.

Since the polymer piezoelectric film is divided and fixed to the holder, even if a crack occurs in the polymer piezoelectric film, the crack can be prevented from progressing.

Hereinafter, it will be explained in detail based on Examples.

(Embodiment) FIG. 1 is a diagram illustrating the configuration of an embodiment of the present invention.

In the figure, 1 is a cylindrical polymer piezoelectric film. The polymer piezoelectric film 1 is stretched in the circumferential direction α as shown in FIG. 3, and then formed into a cylindrical shape as shown in FIG. In this case, polyvinylidene fluoride (PVDF) is used. 11 and 12 are electrodes provided on both sides of the polymer piezoelectric film 1. 1
Lead wires 11 and 121 have one end attached to the electrodes 11 and 12, respectively. Reference numeral 2 denotes a cylindrical holder that holds the polymer piezoelectric membrane 1 so as not to inhibit its respiratory vibration as much as possible. Holder 2
Plastics with excellent weather resistance, such as Teflon and vinyl chloride, are used. 21
are at least two or more recesses each provided in a ring shape along the circumferential surface of the holder 2 in parallel to the axial direction. In this case, two recesses are provided. The recess 21 forms a chamber 3 with the polymer piezoelectric film 1 . Reference numeral 4 denotes a conical reflector whose head side is attached to one end of the polymer piezoelectric film 1, and which imparts directivity to transmitted and received ultrasonic waves. 5 is a chamber 3 provided in the holding body 2;
This is a pressure equalization hole that communicates between the inside and the outside.

In the above configuration, when an electric pulse is applied to the polymer piezoelectric film 1, the polymer piezoelectric film 1 stretches in the stretching direction α
However, since the polymer piezoelectric film 1 is formed in a cylindrical shape, this is converted into a radial breathing vibration. The ultrasound generated by this respiratory vibration is
The direction of travel is changed by the reflector 4, and the beam becomes a doughnut-shaped beam that travels downward in FIG.

On the other hand, if pressure is applied to the polymer piezoelectric film 1 from the outside, the polymer piezoelectric film 1 will expand and contract, causing the electrodes 11, 1
A voltage is generated between the two.

That is, the transducer shown in FIG.
The same operation as in the conventional example shown in the figure is performed.

The polymer piezoelectric film 1 has: (1) low acoustic impedance and easy matching with water, air, etc.;

(2) The internal energy attenuation is large, allowing the transmission and reception of short-duration pulses.

(3) Due to its flexibility, it is easy to manufacture and process into thin films.

It has the following characteristics.

By taking advantage of these characteristics, as shown in FIG. 1, vibrations in the longitudinal direction of the membrane are converted into vibrations in the radial direction.

The resonant frequency f ₀ of the membrane at this time is expressed by equation (2), where R is the radius of curvature of the membrane, C ^E is the elastic modulus, and ρ is the density.

Therefore, hypothetically, C ^E =11.3×10 ⁹ (N/m ² ), ρ=
If it is 1.8×10 ³ (Kg/m ³ ), then in Figure 1,
Approximately 40k by setting the radius of holder 2 to 10mm
It becomes possible to transmit and receive Hz ultrasonic waves.

Hereinafter, the advantages of using the polymer piezoelectric film 1 will be specifically explained in comparison with a ceramic piezoelectric vibrator.

(1) For transmission The absolute value of the sound pressure radiated into the air is proportional to the velocity v of the vibration source if the frequency and radiation area of the vibration source are the same. Since this velocity v is proportional to the displacement x of the vibration source if the frequency is constant, let us consider the conversion efficiency between the voltage V applied to the polymer piezoelectric film 1 and the displacement X.

Electrodes 1 provided on both sides of the polymer piezoelectric film 1
Assuming that a voltage of V is applied between 1 and 12, the extension Δl of the polymer piezoelectric film 1 in the stretching direction, that is, the outer circumference of the cylinder, can be calculated by the following equation.

-Δl/l-=-S-=d ₃₁ E=d・V/t (3) Here, l is the length of the polymer piezoelectric film 1 (=
2πr: r = radius), t is the thickness of the polymer piezoelectric film 1,
d ₃₁ is the piezoelectric strain constant.

From equation (3), Δl becomes larger as the piezoelectric strain constant d ₃₁ becomes larger.
It can be seen that the smaller the thickness t, the larger the value. The larger Δl is, the larger the amplitude X of the respiratory vibration of the polymer piezoelectric membrane 1 is.

The value of the piezoelectric strain constant d ₃₁ of the polymer piezoelectric film 1 is generally about an order of magnitude smaller than the piezoelectric strain constant d ₃₁ of a ceramic piezoelectric vibrator 1a, for example, PZT, but on the contrary, the plate thickness t is extremely small. It is possible to make things. In the end, it is possible to obtain a large Δl/l several times more efficiently than PZT.

To give an example, the piezoelectric strain constant d ₃₁ of the polymer piezoelectric film 1 = 10×10 ^-12 (C/N), the thickness t = 4 μm,
Piezoelectric strain constant d ₃₁ of PZT = 100×10 ^-12 (C/N),
When the thickness t=2 mm, the value of Δl/l is (piezoelectric film/PZT)=5.

In other words, it is impossible to make a cylindrical film with a thickness on the order of 10 μm since ceramic piezoelectric vibrators are susceptible to shock, whereas the polymer piezoelectric film 1 can be made extremely thin. , it is possible to compensate for the small piezoelectric strain constant d ₃₁ .

Since the polymer piezoelectric film 1 is made of a polymer, internal energy attenuation is large. This appears as a high vibration damping effect, and unlike the conventional ultrasonic transducer, there is no need to apply damping using a special damping material 3a.

This further reduces the vibration amplitude due to the damping material 3a (in the conventional example, for example, about 1/
It had decreased to less than 10. ) can be avoided. Considering the difference in efficiency in the above terms, the value of amplitude X obtained when the same voltage V is applied reaches several tens to hundreds of times as large as that of the conventional example.

On the other hand, the transmittance T of energy from the vibrator to the air is expressed as T = 4Z ₁ Z ₂ / (Z ₁ + Z ₂ ) ² (4) Z ₁ ; Acoustic impedance of the vibrator Z ₂ ; Acoustic impedance of the air .

Polymer piezoelectric film Z ₁ 3×10 ⁶ (NS/m ³ ), PZT
Z ₁ 30×10 ⁶ (NS/m ³ ), Z ₂ 400 of air
(NS/m ³ ) is applied, T ₁ /T ₂ =0.53×10 ^-3 /0.053×10 ^-3 = 10 T ₁ ; Transmittance between the polymer piezoelectric film and air T ₂ ; Transmittance between PZT and air In the conventional example using PZT, the acoustic matching layer 2a is used to improve the low transmittance.
However, the polymer piezoelectric film 1 allows propagation with relatively good efficiency even without using such means.

(2) In the case of reception The open end voltage V generated between both surfaces of the polymer piezoelectric film 1 due to the force F (direction is the stretching direction of the polymer piezoelectric film 1) applied from the outside during reception is expressed by the following equation. .

-E-=-V/t-=g ₃₁・σ=g ₃₁・F/
l・t ∴ −V−=g ₃₁・F/l (5) σ; Stress g ₃₁ ; Voltage output constant The value of the voltage output constant g ₃₁ of the polymer piezoelectric film 1 is:
Since the voltage output constant _g31 of ceramics, for example, PZT, is approximately 10 to 200 times larger, a large -V- can be obtained with the same force F.

The effect of the presence or absence of damping material mentioned in the section on transmission also holds true during reception, so overall it is possible to increase efficiency by several tens to twenty times during reception as well.

As a result of the above, according to the device of the present invention, it is possible to achieve functions and transmission/reception efficiency equivalent to or higher than those of the conventional method using a ceramic vibrator, while consuming less than 1/1000 of the power.

Next, the characteristics of the prototype transducer will be explained using a specific example.

Assuming that the radius of the holding body 2 is 10 mm and the height is 30 mm,
In a device in which a polymeric piezoelectric film 1 with a thickness of 50 μm is supported by bonding its upper and lower ends to a holder 2 with a width of 2 mm, the following values are obtained for the transmission and reception sensitivities at a distance of 800 mm in front of the reflector 4. It was done.

Transmission: 120dB (0dB = 2 x 10 ^-4 μbar) Reception: -30dB (0dB = 1V/μbar) This is 500 to 1000 times the total transmission and reception characteristics compared to the conventional transducer shown in Figure 11. It shows improvement.

In the measurement of the transmission sensitivity, the drive voltage of the drive circuit was set to 10Vp-p, and in order to eliminate the invalid component due to the capacitance component of the polymer piezoelectric film 1,
The two are matched with appropriate inductance.

In addition, the thickness of the polymer piezoelectric film 1 was 50 μm in the above specific example, but if this thickness is too thin,
If it is made into a cylindrical shape, it will not be able to maintain its own tension necessary for transmission and reception. In addition, problems arise such as making it difficult to manufacture.On the other hand, if it is too thick, according to equation (3) above,
The problem arises that the transmission sensitivity is reduced.

As a practical value that can be used, 25 to 100 μm is suitable.

In addition, in the embodiment of FIG. 1, the polymer piezoelectric film 1
The reason for fixing only the upper and lower end surfaces is to avoid constraining the breathing vibration of the polymer piezoelectric membrane 1 as much as possible.If constraint points (fixed points) are provided at other locations, the transmitting and receiving sensitivity will be reduced. Decrease rapidly.
That is, for example, as shown in FIG. 4, by only restricting a portion 13 of the side surface of the piezoelectric polymer film 1, the transmitting and receiving sensitivities are reduced to 115 dB for transmitting and -35 dB for receiving, respectively.

That is, by fixing only the upper and lower ends of the polymer piezoelectric film 1 to the holder 2, a highly sensitive film can be obtained.

FIG. 6 is a graph comparing the total transmitting and receiving sensitivity with and without the pressure equalizing hole 5 in the configuration of FIG. 1. indicates the case where there is no pressure equalizing hole 5, and indicates the case where there is the pressure equalizing hole 5.

If the pressure increases due to changes in ambient pressure,
When there is no pressure equalizing hole 5, the sensitivity rapidly decreases as the pressure increases, whereas when there is a pressure equalizing hole 5, no decrease in sensitivity occurs.

FIG. 7 shows the directivity indicating the magnitude of the reflected sound from the reflector 4 at a distance of 3 m in front of the transducer.

Due to the effect of the reflector 4, sharp directivity with a half angle of less than 4° can be obtained, making it possible to achieve ideal characteristics as a distance meter or a level meter.

The drawback of the transducer of an ultrasonic distance meter using the polymer piezoelectric film 1 is that the mechanical strength of the polymer piezoelectric film 1 itself is low.

This is particularly problematic when used in industrial sensors where harsh conditions must be considered. In this case, it is necessary to prevent a crack that has occurred at one location in the piezoelectric polymer film 1 from progressing to the entire piezopolymer film 1 and causing a fatal injury.

In the present invention, the polymer piezoelectric film 1 is divided and fixed to the holder 2 by providing two recesses 21, so that even if a crack occurs, the progress of the crack can be stopped and the crack can be prevented. It is possible to prevent fatal injuries caused by

In this case, the reception sensitivity of the distance meter will be reduced, but there will be no functional problem. That is, in a rangefinder, the reception level typically varies significantly.
Therefore, the receiving circuit is configured to cope with this.

As a result (1) Since the internal attenuation of the polymer piezoelectric film 1 itself is large, it becomes possible to transmit and receive ultrasonic waves with high damping characteristics without using a damping material.

(2) Since no damping material is used, there is no energy loss and highly efficient transmission and reception is possible.

(3) The acoustic impedance of the polymer piezoelectric film 1 is one order of magnitude smaller than the acoustic impedance of the ceramic vibrator, so the efficiency of transmitting and receiving sound into the air is good.

(4) Since the thickness of the polymer piezoelectric film 1 can be made thinner, the electric field strength can be increased during transmission.
The transmission efficiency (the amount of displacement of the polymer piezoelectric film 1) can be increased.

Also, during reception, this thinness does not affect the output. On the other hand, due to the high voltage output constant g ₃₁ of the polymer piezoelectric film 1 itself, a high open circuit voltage can be obtained.

That is, it is possible to greatly improve both transmission and reception efficiency.

(5) Since there is no need to use damping materials, acoustic matching layers, etc., changes in temperature characteristics caused by changes in these physical properties can be avoided.

(6) Therefore, compared to the conventional example shown in FIG. 11, high performance can be achieved with extremely low power consumption.

(7) Since the polymeric piezoelectric film 1 is fixed only to the upper and lower end surfaces, unrestricted and free breathing vibrations can be obtained, and as a result, high transmitting and receiving sensitivity can be obtained.

(8) By having the pressure equalizing hole 5, it is possible to realize a transducer whose sensitivity is not affected by ambient pressure.

(9) By using the reflector 4, it is possible to realize a transducer with good directivity, which is suitable for use in a rangefinder.

(10) Since two recesses 21 are provided in the holder 2 and the polymer piezoelectric film 1 is divided and fixed, even if a crack occurs in the polymer piezoelectric film 1, the progress of the crack can be stopped. This can prevent fatal injuries caused by cracks.

FIG. 8 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, there are four recesses 21 and a holding body 2.
It is set to 0. This is intended to prevent the progression of cracks in the polymer piezoelectric film 1 to a smaller extent.
The reliability of the instrument can be further improved.

FIG. 9 and FIG. 10 are configuration explanatory diagrams of other embodiments of the present invention.

In this embodiment, a protection plate 6 is disposed at the center of the opening of the reflector 4, perpendicular to the axis of the holder 2, so as not to obstruct the path of the ultrasonic signal.
Reference numeral 7 denotes a soot ring-shaped net that connects the protective plate 6 and the opening edge of the reflector 4 and transmits ultrasonic waves. The net 7 has a wire diameter and density such that reflection of ultrasonic waves can be ignored.

In this embodiment, it is possible to protect the polymer piezoelectric film 1 from forces directly applied to it, such as from being touched strongly by hand or from being touched by a sharp object.

In the above embodiment, the holder 2 was described as being made of plastic material, but it may also be made of metal such as stainless steel and used also as the electrode extension part (lead part) from the inner electrode of the polymer piezoelectric film 1. Of course it's a good thing.

In addition, if the material of the holder 2 is made of ceramics such as alumina, it is possible to integrally fire a complex shape, and additional machining can be kept to a minimum.
Manufacturing costs can be reduced.

Ceramics also have excellent weather resistance and chemical resistance.

Furthermore, if a metal coating (metallizing) is applied to the ceramic surface, an additional advantage can be added that this can be used as a lead-out portion of the inner electrode.

In addition, in the above-mentioned embodiment, it was explained that the polymer piezoelectric film 1 is made of polyvinylidene fluoride (PVDE), but it is not limited to this, and for example,
Copolymer of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)), copolymer of vinylidene fluoride and tetrafluoroethylene (P(VDF-TrFE))
TeFE)) or an alternating copolymer of cyanovinylidene and vinyl acetate (P(VDCN-VAc)) may be used, as long as it exhibits good piezoelectricity. These materials do not necessarily require a stretching operation, and only a polarization operation by applying a high voltage may be sufficient.

Further, in the above-mentioned embodiment, the recess 21 has two
Although it has been explained that two or four are provided, it is needless to say that the number is not limited to this.

(Effects of the Invention) As explained above, the present invention includes a cylindrical holder, which is separated from each other in the axial direction of the holder, and each of which covers the entire circumference of the circumferential surface of the holder. At least two or more recesses provided in a ring shape across the holder, and a portion provided to cover the outer peripheral surface of the holder and in contact with the peripheral surface of the holder other than the portion where the recess is formed is fixed, and the recess a cylindrical polymer piezoelectric film whose portion facing the concave portion forms a ring-shaped chamber; an electrode plate provided on the outer peripheral surface and inner peripheral surface of the polymer piezoelectric film, respectively; and one end of the holder. a conical reflecting umbrella that is attached to the head side of the holding body and imparts directivity in the axial direction of the holding body to the transmitted and received ultrasonic waves;
A transducer for an ultrasonic distance meter was constructed, which included a pressure equalizing hole provided in the holder and having one end open to the chamber and the other end open to the outside.

As a result, (1) since the internal attenuation of the polymer piezoelectric film itself is large, it is possible to transmit and receive ultrasonic waves with high damping characteristics without using a damping material. (2)
Since no damping material is used, there is no energy loss and highly efficient transmission and reception is possible. (3) The acoustic impedance of the polymer piezoelectric film is one order of magnitude smaller than that of the ceramic vibrator, so it transmits and receives sound into the air with good efficiency. (4) Since the thickness of the polymer piezoelectric film can be reduced, the electric field strength can be increased during transmission, and the transmission efficiency (the amount of displacement of the polymer piezoelectric film) can be increased.
Also, during reception, this thinness does not affect the output. On the other hand, a high open circuit voltage can be obtained due to the high voltage output constant g ₃₁ of the polymer piezoelectric film itself. That is, it is possible to greatly improve both transmission and reception efficiency. (5) Since there is no need to use damping materials, acoustic matching layers, etc., changes in temperature characteristics caused by changes in these physical properties can be avoided.
(6) Therefore, compared to the conventional example, high performance can be achieved with extremely low power consumption. (7) Since the polymer piezoelectric membrane is fixed only to the upper and lower end faces, unrestricted and free breathing vibrations can be obtained, and as a result, high transmitting and receiving sensitivity can be obtained. (8) By having a pressure equalizing hole, it is possible to realize a transducer whose sensitivity is not affected by ambient pressure. (9) By using a reflector, it is possible to realize a transducer with good directivity, which is ideal for use in distance meters. (10) Since two recesses are provided in the holder to divide and fix the polymer piezoelectric film, even if a crack occurs in the polymer piezoelectric film, the crack can be stopped from progressing. This can prevent fatal injuries.

Therefore, according to the present invention, it is possible to realize an ultrasonic transducer with a simple structure, high damping characteristics, good efficiency, robustness, and high reliability.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, and FIG.
The figure is a plan view of FIG. 1, FIG. 3 is an explanatory diagram of parts of FIG. 1, FIGS. 4 to 7 are explanatory diagrams of operation of FIG. 1, and FIG. 8 is a configuration of another embodiment of the present invention. Explanatory drawings, FIG. 9 is a configuration explanatory diagram of another embodiment of the present invention, FIG. 10 is a plan view of FIG. 9, FIG. 11 is a configuration explanatory diagram of a conventional example commonly used, and FIG. The figure is the first
1 is a plan view, and FIG. 13 is an explanatory diagram of the operation of FIG. 11. 1... Polymer piezoelectric film, 11, 12... Electrode, 1
11, 121... Lead wire, 2, 20... Holder, 21... Recess, 3... Chamber, 4... Reflector, 5
...Pressure equalization hole, 6...Protection plate, 61...Sound absorption plate, 7
...net.

Claims (1)

[Scope of Claims] 1. A cylindrical holder, each of which is provided in a ring shape over the entire circumferential circumference of the holder, which are separated from each other in the axial direction of the holder. At least two or more recesses, a portion provided to cover the outer peripheral surface of the holder, a portion in contact with the peripheral surface of the holder other than the portion where the recess is formed is fixed, and a portion facing the recess is the recess. A cylindrical polymer piezoelectric film forming a ring-shaped chamber, electrode plates provided on the outer and inner peripheral surfaces of the polymer piezoelectric film, and a head side attached to one end of the holder for transmitting and receiving. A conical reflecting umbrella that imparts directivity in the axial direction of the holding body to the ultrasonic waves; and a pressure equalizing hole provided in the holding body and having one end opening into the chamber and the other end opening outside. A transducer for an ultrasonic distance meter.