CN100462694C - Ultrasonic transmitter-receiver and ultrasonic flowmeter - Google Patents

Ultrasonic transmitter-receiver and ultrasonic flowmeter Download PDF

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Publication number
CN100462694C
CN100462694C CNB2007100052966A CN200710005296A CN100462694C CN 100462694 C CN100462694 C CN 100462694C CN B2007100052966 A CNB2007100052966 A CN B2007100052966A CN 200710005296 A CN200710005296 A CN 200710005296A CN 100462694 C CN100462694 C CN 100462694C
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China
Prior art keywords
matching layer
acoustic matching
ultrasonic transmitter
receiver
piezoelectrics
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CN101033992A (en
Inventor
永原英知
桥本雅彦
铃木正明
桥本和彦
桥田卓
白石诚吾
高原范久
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters

Abstract

An acoustic matching layer according to the present invention includes a powder of a dry gel. The dry gel preferably has a density of 500 kg/m<3> or less and an average pore diameter of 100 nm or less. By using the dry gel powder, a variation in the property of the acoustic matching layer can be reduced.

Description

Ultrasonic transmitter-receiver and ultrasonic flow meter
Technical field
The invention relates to ultrasonic transmitter-receiver and manufacture method thereof with acoustic matching layer, and the ultrasonic flow meter that is provided with this ultrasonic transmitter-receiver.
Background technology
In recent years, measure in the pipe that the ultrasonic transmission fluid flows through the both time of set a distance, by measuring the translational speed of fluid, in gas instrument etc., obtained utilization based on the ultrasonic flow meter of this flowing velocity decision flow.
Figure 35 is the cross section structure of the major part of the such ultrasonic flow meter of expression.Ultrasonic flow meter disposes to such an extent that the determined object data stream body that should measure flow can be flowed in pipe.On tube wall 102, opposite face is provided with a pair of ultrasonic transmitter-receiver 101a, 101b.Ultrasonic transmitter-receiver 101a, 101b use the piezoelectric vibrators such as piezoelectric ceramics as electric energy/mechanical energy conversion element to constitute, and show and piezoelectric buzzer and the same resonance characteristics of piezoelectric oscillator.
Under state shown in Figure 35, ultrasonic transmitter-receiver 101a is used as ultrasound transmitter device, and ultrasonic transmitter-receiver 101b is used as ultrasonic receiver.
To have near the alternating voltage of the frequency resonant frequency with ultrasonic transmitter-receiver 101a when putting on piezoelectrics (piezoelectric vibrator) in the ultrasonic transmitter-receiver 101a, ultrasonic transmitter-receiver 101a has the function as ultrasound transmitter device, radiates ultrasound wave in fluid.The ultrasound wave of radiation is propagated through path L1, arrives ultrasonic transmitter-receiver 101b.At this moment, ultrasonic transmitter-receiver 101b has the function as receiver, receives ultrasound wave and is transformed to voltage.
Then, this time ultrasonic transmitter-receiver 101b has the function as ultrasound transmitter device, and ultrasonic transmitter-receiver 101a has the function as ultrasonic receiver.That is to say, put on piezoelectrics in the ultrasonic transmitter-receiver 101b, make and to fluid, radiate ultrasound wave from ultrasonic transmitter-receiver 101b by alternating voltage with near the frequency the resonant frequency of ultrasonic transmitter-receiver 101b.The ultrasound wave of radiation is propagated through path L2, arrives ultrasonic transmitter-receiver 101a.Ultrasonic transmitter-receiver 101a receives and propagates the ultrasound wave that comes and be transformed to voltage.
Like this, because ultrasonic transmitter-receiver 101a and 101b can play the function as transmitter and receiver alternately, so generally be generically and collectively referred to as ultrasonic transmitter-receiver (or the ultrasound wave transmission connects wave-receiver).
In ultrasonic flow meter shown in Figure 35, because when applying continuous alternating voltage, from the continuous ultrasound wave of ultrasonic transmitter-receiver radiation, be difficult to measure the time of propagation, so use usually with pulse signal as the short burst voltage signal of propagation wave as driving voltage.
Below the measuring principle of above-mentioned ultrasonic flow meter is described in detail.
Put on ultrasonic transmitter-receiver 101a by the short burst voltage signal that will drive usefulness, from ultrasonic transmitter-receiver 101a radiation ultrasound wave burst signal the time, the ultrasound wave burst signal is propagated through path L1, and t arrives ultrasonic transmitter-receiver 101b after the time.Make the distance of path L1 same with the distance of path L2.
Ultrasonic transmitter-receiver 101b can be transformed to electric pulse signal than only propagating the ultrasound wave short pulse signal that comes with high S/N.This electric pulse signal is carried out electric amplification, put on ultrasonic transmitter-receiver 101a again, radiation ultrasound wave short pulse signal.The device that will move like this is called " sound circular form device ".And, will be after ultrasonic transmitter-receiver 101a radiation ultrasonic pulse be called " cycle period " to the time that arrives ultrasonic transmitter-receiver 102b.The inverse of " sound cycle period " is called " sound cycle frequency ".
In Figure 35, being located at the flow rate of fluid that flows in the pipe is V, and the angle of the direction of propagation of the hyperacoustic speed C in the fluid, the flow direction of fluid and ultrasonic pulse is θ.Using ultrasonic transmitter-receiver 101a as ultrasound transmitter device, when using ultrasonic transmitter-receiver 101b as ultrasonic receiver, if the ultrasonic pulse that sends from ultrasonic transmitter-receiver 101a arrives the time of ultrasonic transmitter-receiver 101b, promptly the sound cycle period is t1, the sound cycle frequency is f1, then has following formula (1) to set up.
f1＝1/t1＝(C+Vcosθ)/L (1)
Otherwise if using ultrasonic transmitter-receiver 101b to be t2 as ultrasound transmitter device, sound cycle period when using ultrasonic transmitter-receiver 101 as ultrasonic receiver, the sound cycle frequency is f2, and following formula (2) establishment is then arranged.
f2＝1/t2＝(C—Vcosθ)/L (2)
The difference on the frequency Δ f of two cycle frequencys is represented by following formula (3).
Δf＝f1—f2＝2Vcosθ/L (3)
According to formula (3), can obtain flow rate of fluid V from the distance L and the difference on the frequency Δ f of ultrasonic propagation.And, from this flow velocity V, can determine flow.
In such ultrasonic flow meter, can obtain high precision.In order to improve precision, the acoustic impedance that the ultrasound wave of the piezoelectrics in ultrasonic transmitter-receiver sends the acoustic matching layer that forms on the receiving plane is important.Acoustic matching layer particularly radiates under hyperacoustic situation and is receiving to gas at ultrasonic transmitter-receiver and propagated under next hyperacoustic situation by gas, plays an important role.
Below, with reference to Figure 36, the effect of acoustic matching layer is illustrated.Figure 36 represents the cross section structure of ultrasonic transmitter-receiver 103 always.
Illustrated ultrasonic transmitter-receiver 103 is provided with at the fixing piezoelectrics 106 in the inboard of sensor box 105, with the acoustic matching layer of fixing in the outside of sensor box 105 104.Acoustic matching layer 104 is bonding with sensor box 105 by cementing agent of epoxy resin etc.Equally, piezoelectrics 106 are also bonding with sensor box 105.
The ultrasonic vibration of piezoelectrics 106 is passed to sensor box 106 by tack coat, and then passes to acoustic matching layer 104 by another tack coat.Thereafter, ultrasonic vibration is radiated as sound wave to the gas (ultrasonic propagation medium) that joins with acoustic matching layer 104.
The effect of acoustic matching layer 104 is that the vibration with piezoelectrics propagates into gas effectively.Below this point is described in detail.
The acoustic impedance Z of material is to use the velocity of sound C in this material and the density p of material, is defined by following formula (4).
Z＝ρ×C (4)
As the acoustic impedance of the gas of ultrasonic wave radiation object, be very different with the acoustic impedance of piezoelectrics.The acoustic impedance Z1 of general piezoelectrics PZT piezoelectric ceramics such as (lead zirconate titanate) is about 30 * 106kg/m 2/ s.In contrast to this, the acoustic impedance Z3 of air is about 400kg/m 2/ s.
At the boundary face of the different material of acoustic impedance, sound wave reflects easily, makes the strength degradation through the sound wave of boundary face.Therefore, between piezoelectrics and gas, insertion has the material of acoustic impedance Z2 as the formula (5).
Z2＝(Z1×Z3) 1/2 (5)
Insertion has the material of such acoustic impedance Z2, can be suppressed at the reflection of boundary face, and the transmitance of sound wave is improved.
At acoustic impedance Z1 is 30 * 10 6Kg/m 2/ s, acoustic impedance Z3 are 400kg/m 2Under the situation of/s, the acoustic impedance Z2 that satisfies formula (5) is about 11 * 10 4Kg/m 2/ s.Have 11 * 10 4Kg/m 2The material of the value of/s must satisfy formula (4), i.e. Z2=ρ * C certainly.In solid material, find out very difficulty of such material.Its reason is because to require be that solid, density p will be fully little and velocity of sound C is fully little.
Now, as the material of acoustic matching layer, be extensive use of by the resin material material that glass bead and baton round etc. are fixing.And, as the method for making of such material that is suitable for acoustic matching layer,, for example in No. 2559144 communique of special permission, explanation is arranged with the method for the glass bead hot compression of hollow and with the method for melted material foaming etc.
Summary of the invention
Yet the acoustic impedance of these materials is greater than 50 * 10 4Kg/m 2/ s can satisfy formula (5) hardly.In order to obtain highly sensitive ultrasonic transmitter-receiver, be necessary to form acoustic matching layer by the littler material of acoustic impedance.
In order to satisfy such requirement, the present inventor has invented and can fully satisfy the acoustic matching material of formula (5), is willing to describe in detail in the flat 2001-056051 instructions the spy.These materials are to use the desiccant gel made of having given permanance, and density p is littler, and velocity of sound C is lower.
Be provided with ultrasonic transmitter-receiver by the extremely low formed acoustic matching layers of material such as desiccant gel of such acoustic impedance, can carry out hyperacoustic transmission and reception with gas in high sensitivity, the result is the device that obtains carrying out gas flow high-acruracy survey.
But, the material that acoustic impedances such as desiccant gel are extremely low, common mechanical intensity is also low.Particularly, though desiccant gel is more intense to the stress on the compression direction, to stretch and the stress of bending direction extremely a little less than, it is just destroyed easily to be subjected to weak impulsive force.
And, because the velocity of sound of such material is very low, thus for the suitable acoustic matching layer thickness that obtains maximum transmission receiving sensitivity (send receive wavelength about 1/4) just thin in the extreme.For example, if the velocity of sound of material is 60～400m/s, under the situation of carrying out hyperacoustic transmission about 500vHz and reception, the thickness of preferred acoustic matching layer is 30～200 μ m.For so thin acoustic matching layer, acoustic matching layer is just very difficult as an operation of components, to bonding acoustic matching layers such as sensor box and piezoelectrics, making ultrasonic transmitter-receiver almost is impossible, even or may, from the viewpoint of fabrication yield and cost, also be difficult to practicability.
And then, because the physical strength of acoustic matching layer is low, so in the process of using as ultrasonic transmitter-receiver, ultrasonic vibration self may be brought out peeling off of acoustic matching layer etc., might make reliability decrease.
The present invention proposes in view of the above problems, its purpose is to provide a kind of ultrasonic transmitter-receiver and manufacture method thereof, can when being set, can make on the yield rate highland the formed acoustic matching layer of material low by physical strengths such as desiccant gels, that the velocity of sound is low, and the reliability height.
Another object of the present invention provides the ultrasonic flow meter that is provided with above-mentioned ultrasonic transmitter-receiver.
Ultrasonic transmitter-receiver of the present invention has piezoelectrics, the acoustic matching layer that on described piezoelectrics, is provided with, and contact, be arranged at protection portion for the fixing position of described piezoelectrics with at least a portion of the side of described acoustic matching layer.
In preferred embodiment, described protection portion is from outstanding to the ultrasonic wave radiation direction on the plane of same level with the interarea of described piezoelectrics, is the thickness that the height of the described protection portion of benchmark is stipulated described acoustic matching layer with the interarea of described piezoelectrics.
In preferred embodiment, the described height of described protection portion is below the above 2500 μ m of 5 μ m.
In preferred embodiment, the thickness of described acoustic matching layer equates substantially with the described height of described protection portion.
In preferred embodiment, the thickness of described acoustic matching layer is about 1/4 of the ultrasound wave wavelength that sent and/or received by described piezoelectrics.
In preferred embodiment, described acoustic matching layer is to be 50kg/cm by density 3Above 1000kg/cm 3Following material forms.
In preferred embodiment, described acoustic matching layer is to be 2.5 * 10 by acoustic impedance 3Kg/m 2/ s above 1.0 * 10 6Kg/m 2The following material of/s forms.
In preferred embodiment, described acoustic matching layer is formed by inorganic based material.
In preferred embodiment, described inorganic based material is the desiccant gel of inorganic oxide.
In preferred embodiment, described inorganic oxide has hydrophobization solid bone portion.
In preferred embodiment, described acoustic matching layer be on the described piezoelectrics that are provided with described protection portion by mobile state solidified material.
In preferred embodiment; has the lower floor's acoustic matching layer that between the interarea of described piezoelectrics and described acoustic matching layer, is provided with; described protection portion is outstanding from the interarea of described second sound matching layer, is the thickness that the height gage of the described protection portion of benchmark is positioned the described acoustic matching layer of the superiors with the interarea of described acoustic matching layer.
In preferred embodiment, described protection portion is made of the part institute of described lower floor acoustic matching layer, and is integrated with described lower floor acoustic matching layer.
In preferred embodiment, the described height of described protection portion is below the above 2500 μ m of 5 μ m.
In preferred embodiment, the described height of described protection portion equates substantially with the thickness of the described acoustic matching layer that is positioned at the superiors.
In preferred embodiment, described first acoustic matching layer and described lower floor acoustic matching layer have about 1/4 thickness of the ultrasound wave wavelength that sent and/or received by described piezoelectrics respectively.
In preferred embodiment, the density of described first acoustic matching layer is 50kg/cm 3Above 1000kg/cm 3Below.
In preferred embodiment, the acoustic impedance of described lower floor acoustic matching layer is 2.5 * 10 greater than the acoustic impedance of described first acoustic matching layer 3Kg/m 2/ s above 3.0 * 10 7Kg/m 2Below/the s.
In preferred embodiment, described protection portion is present in the periphery of the described acoustic matching layer that is positioned at the superiors.
In preferred embodiment, described protection portion covers circumferential lateral surface all of the described acoustic matching layer that is positioned at the superiors.
In preferred embodiment, described protection portion is disposed at the outside of the interarea of described piezoelectrics.
In preferred embodiment, described protection portion is arranged on the interarea of described piezoelectrics.
In preferred embodiment, described protection portion is arranged on the described lower floor acoustic matching layer.
In preferred embodiment, described protection portion is formed by the part of described lower floor acoustic matching layer, and is integrated with described lower floor acoustic matching layer.
In preferred embodiment, and then be provided with the structural support that supports described piezoelectrics.
In preferred embodiment, and then be provided with the structural support that supports described piezoelectrics, described protection portion is arranged on the described structural support.
In preferred embodiment, described structural support is made of pressure-formed metal, and described protection portion is made of the part crooked by the pressure forming of described structural support.
In preferred embodiment, the described height of described protection portion is below the above 2500 μ m of 5 μ m.
In preferred embodiment, the thickness of described acoustic matching layer equates substantially with the described height of described protection portion.
In preferred embodiment, the thickness of described acoustic matching layer is about 1/4 of the ultrasound wave wavelength that sent and/or received by described piezoelectrics.
In preferred embodiment, the density of described acoustic matching layer is 50kg/m 3Above 1000kg/m 3Below.
In preferred embodiment, the acoustic impedance of described acoustic matching layer is 2.5 * 10 3Kg/m 2/ s above 1.0 * 10 6Kg/m 2Below/the s.
In preferred embodiment, and then be provided with the back side load parts at the back side that is configured in described piezoelectrics, described guard block is arranged on the load parts of the described back side.
In preferred embodiment, described protection portion is that the part institute by described back side load parts is constituted, and is integrated with described back side load parts.
In preferred embodiment, at least a portion of the surface of contact of described acoustic matching layer and described protective seam receives the surface treatment of giving hydroxyl.
In preferred embodiment, at least a portion of the surface of contact of described acoustic matching layer and described protective seam receives the asperities processing.
In preferred embodiment, at least a portion of the surface of contact of described acoustic matching layer and described protective seam is a porous matter.
In preferred embodiment, in ultrasonic transmitter-receiver with the contacted part of described sound equipment conformable layer, a part of soaking into described sound equipment conformable layer, and integrated.
Another kind of ultrasonic transmitter-receiver of the present invention has: the piezoelectrics that carry out ultrasonic vibration; By density is 50kg/m 3Above 1000kg/m 3Below and acoustic impedance be 2.5 * 10 3Kg/m 2/ s above 1.0 * 10 6Kg/m 2The formed upper strata of the material acoustic matching layer that/s is following; The lower floor's acoustic matching layer that between described piezoelectrics and described upper strata acoustic matching layer, is provided with; Support described lower floor acoustic matching layer and described piezoelectrics and cover described piezoelectrics, wherein be provided with the contacted protection of at least a portion portion with the side of described upper strata matching layer with the structural support that itself and ultrasonic propagation fluid separate.
Described protection portion is formed by the part of described lower floor acoustic matching layer, and is integrated with described lower floor acoustic matching layer.
In preferred embodiment, the elastic modulus of described protection portion equates substantially with the elastic modulus of described acoustic matching layer.
Ultrasonic flow meter of the present invention is provided with: the flow measurement portion that determined fluid flows through; Be arranged at a pair of ultrasonic transmitter-receiver of described flow measurement portion, transmission and received ultrasonic signal; The measurement mechanism in travel-time of measuring ultrasound wave between described a pair of ultrasonic transmitter-receiver; And based on the flow routing device of the calculated signals outflow of described measurement mechanism, described a pair of ultrasonic transmitter-receiver is respectively above-mentioned any ultrasonic transmitter-receiver.
In preferred embodiment, cover the piezoelectrics of described ultrasonic transmitter-receiver, itself and described determined fluid are cut off.
The feature of device of the present invention is to be provided with above-mentioned any ultrasonic transmitter-receiver.
The manufacture method of ultrasonic transmitter-receiver of the present invention, comprise the operation (a) of preparing to have interarea and the piezoelectrics of the protuberance that on described interarea, is provided with, and on the interarea of described piezoelectrics, form acoustic matching layer, make at least a portion of side of described acoustic matching layer and the contacted operation in side (b) of described protuberance.
In preferred embodiment, described operation (b) comprises the operation of gel raw material supplying to the interarea of described piezoelectric element, and by drying and the operation that is solidified to form described acoustic matching layer with described gel raw material.
In preferred embodiment, described operation (a) comprises the surface that processes piezoelectrics, forms the operation of described interarea and protuberance.
In preferred embodiment, described operation (a) is included in the operation of the described protuberance of surperficial fixed engagement of piezoelectrics.
In preferred embodiment, described operation (a) comprises the operation of piezoelectrics fixed engagement in structural support.
The method of ultrasonic transmitter-receiver of the present invention, be to make to be provided with the upper strata acoustic matching layer, piezoelectrics, and the method for the ultrasonic transmitter-receiver of the lower floor's acoustic matching layer that between described upper strata acoustic matching layer and described piezoelectrics, is provided with, this method comprise prepare to have recess, as the operation (a) of the parts of described lower floor acoustic matching layer function, the recess of described parts is supplied with the operation (b) of gel raw material, and by drying and the operation (c) that is solidified to form described upper strata acoustic matching layer with described gel raw material.
In preferred embodiment, described operation (b) comprises makes described gel raw material soak into the operation of described parts.
In preferred embodiment, described gel raw material soaks into all of described parts.
In preferred embodiment, described operation (b) is to carry out after the configuration relation of described parts and described piezoelectrics is fixing.Described operation (b) also can be carried out before the configuration relation of described parts and described piezoelectrics is fixing.
Ultrasonic transmitter-receiver of the present invention is provided with piezoelectrics, the acoustic matching layer that on described piezoelectrics, is provided with, and join with the outer peripheral face of described acoustic matching layer and the protection portion that disposes.
Ultrasonic transmitter-receiver of the present invention is provided with structural support, the described structural support of clamping, the piezoelectrics and the acoustic matching layer that are provided with of position over there, and join with the outer peripheral face of described acoustic matching layer and the protection portion that disposes.
Among the present invention and then other ultrasonic transmitter-receiver, be to be provided with piezoelectrics with the interarea that carries out hyperacoustic transmission and/or reception, ultrasonic transmitter-receiver with the acoustic matching parts that on the interarea of described piezoelectrics, are provided with, described acoustic matching parts have first acoustic matching part and are lower than described first acoustic matching second compatible portion partly with average density, and described first acoustic matching part contacts with the side of described second compatible portion.
In preferred embodiment, described first acoustic matching part is thicker than described second sound compatible portion, from the radiation of the interarea of described piezoelectrics, see through hyperacoustic phase place of second sound compatible portion, arrival and same level position above described first acoustic matching part, with from described interarea radiation, see through described first acoustic matching part and arrive described first acoustic matching partly above hyperacoustic phase place unanimous on the whole.
In preferred embodiment, when hyperacoustic wavelength was λ 1 in described first acoustic matching part, the thickness of described first acoustic matching part had the size of k1 λ 1 (k1 is more than 1/8, below 1/3), and different with the thickness of described the 21st acoustic matching part.
In preferred embodiment, described second sound compatible portion is made of N layer acoustic matching layer (N is the integer more than 1), and the acoustic matching layer of N layer has the k2 size (k2 is more than 1/8, below 1/3) doubly of hyperacoustic wavelength described in each acoustic matching layer separately.
In preferred embodiment, be positioned at the thickness of the outermost acoustic matching layer of described second sound compatible portion, be approximately be positioned at described second sound compatible portion outermost acoustic matching layer ultrasound wave wavelength 1/4.
In preferred embodiment, in the described second sound compatible portion,, be to constitute by material identical materials with described first acoustic matching part at the nearest formed acoustic matching layer in position of interarea of the described piezoelectrics of distance.
In preferred embodiment, in the described second sound compatible portion,, be integrally formed with the described first acoustic matching part at the nearest formed acoustic matching layer in position of interarea of the described piezoelectrics of distance.
In preferred embodiment, the acoustic matching layer of one deck at least that is comprised in the described second sound compatible portion is formed by desiccant gel.
In preferred embodiment, described desiccant gel is made of inorganic based material.
In preferred embodiment, described desiccant gel has hydrophobization solid bone portion.
In preferred embodiment, in the parts that constitute the sound wave transmitter-receiver,, be asperities or porous matter with at least a portion of described acoustic matching part abutted surface.
In preferred embodiment, in parts and at least a portion described second sound compatible portion abutted surface that constitutes the sound wave transmitter-receiver, the part of described second sound compatible portion is soaked into integrated to described parts.
In preferred embodiment, at least a portion of described second sound compatible portion is formed by desiccant gel, and described first acoustic matching is formed by the physical strength material higher than described desiccant gel.
In preferred embodiment, at least a portion of described first acoustic matching part is formed by porous ceramics.
In preferred embodiment, the thickness of described first acoustic matching part changes corresponding to the position in the interarea of described piezoelectrics.
In preferred embodiment, the thickness of described second sound compatible portion changes corresponding to the position in the interarea of described piezoelectrics.
Ultrasonic flow meter of the present invention, be to be provided with the flow measurement portion that determined fluid flows through, be arranged at a pair of ultrasonic transmitter-receiver of described flow measurement portion, transmission and received ultrasonic signal, measure the measurement mechanism of the time that ultrasound wave propagates between described a pair of ultrasonic transmitter-receiver, and based on the ultrasonic flow meter of the flow routing device of the calculated signals outflow of described measurement mechanism, described a pair of ultrasonic transmitter-receiver is respectively above-mentioned any ultrasonic transmitter-receiver.
In preferred embodiment, the piezoelectrics of described ultrasonic transmitter-receiver are covered, itself and described determined fluid are separated.
In preferred embodiment, described determined fluid is a gas.
Device of the present invention is provided with above-mentioned any ultrasonic transmitter-receiver.
The manufacture method of ultrasonic transmitter-receiver of the present invention, comprise (a) prepare to have first and with second of described first opposite side, on described first and second, formed the operation of the piezoelectrics of electrode, (b) form the operation of second sound compatible portion at least one side's side of described first and second of described piezoelectrics, (c) operation of supply gel raw material in by described piezoelectrics and the formed space of second sound compatible portion, (d) gelation of described gel material liquid is obtained the operation of moistening gel, and the operation of the moistening gel drying that (e) will obtain.
In preferred embodiment, described operation (c) comprises: operation from the first gel raw material to described space that (c1) supply with, (c2) with the described first gel material liquid gelation, form the operation of the first moistening gel layer, (c3) on the described first moistening gel layer, supply with the operation of the second gel raw material, and (c4) will the described second gel material liquid gelation, the operation of the formation second moistening gel layer.Described (e) operation comprises by the drying to described first and second moistening gel layer, is formed the operation of first acoustic matching layer and second sound matching layer respectively by described first and second moistening gel layer.
In preferred embodiment, in described operation (c4),, the acoustic impedance of described first acoustic matching layer is changed to the described first moistening gel layer upgrading.
Ultrasonic transmitter-receiver of the present invention, be to be provided with piezoelectrics with the interarea that carries out hyperacoustic transmission and/or reception, and the ultrasonic transmitter-receiver of the acoustic matching parts that on the interarea of described piezoelectrics, are provided with, described acoustic matching parts have the first acoustic matching part, with the second sound compatible portion that the physical strength lower than the physical strength of first acoustic matching part arranged, described first acoustic matching part contacts with the side of described second sound compatible portion.
Description of drawings
Fig. 1 is the sectional view of ultrasonic transmitter-receiver in expression first embodiment of the present invention.
Fig. 2 is the vertical view of ultrasonic transmitter-receiver in first embodiment of the present invention.
Fig. 3 (a) is the figure that the transmission of ultrasonic transmitter-receiver in expression first embodiment of the present invention receives waveform, and Fig. 3 (b) represents that the transmission of ultrasonic transmitter-receiver always receives the figure of waveform.
Fig. 4 is that acoustic matching layer shrinks the pattern sectional view of situation in expression first embodiment of the present invention.
Fig. 5 is the sectional view of ultrasonic transmitter-receiver in the second embodiment of the invention.
Fig. 6 is the sectional view of other structure of protection portion in the expression second embodiment of the invention.
Fig. 7 is the top figure of other structure of protection portion in the expression second embodiment of the invention.
Fig. 8 is the sectional view of ultrasonic transmitter-receiver in the third embodiment of the invention.
Fig. 9 is the sectional view of ultrasonic transmitter-receiver in the four embodiment of the invention.
Figure 10 is the sectional view of ultrasonic transmitter-receiver in the fifth embodiment of the invention.
Figure 11 (a) is the figure that the transmission of ultrasonic transmitter-receiver in expression the 5th embodiment of the present invention receives waveform, and Figure 11 (b) represents that the transmission of ultrasonic transmitter-receiver always receives the figure of waveform.
Figure 12 is the figure of other structures of lower floor's acoustic matching layer in the expression sixth embodiment of the invention.
Figure 13 is the sectional view of ultrasonic transmitter-receiver in the seventh embodiment of the invention.
Figure 14 is the figure that the transmission of ultrasonic transmitter-receiver in expression the 7th embodiment of the present invention receives waveform.
Figure 15 is the sectional view of the ultrasonic transmitter-receiver of other structure in the seventh embodiment of the invention.
Figure 16 (a) is the operation sectional view of the manufacture method of expression ultrasonic transmitter-receiver shown in Figure 12 to Figure 16 (c).
Figure 17 (a) is in operation shown in Figure 16, and the expression gel soaks into the sectional view of the acoustic matching layer under the sufficient situation, (b) is that the expression gel soaks into the sectional view under the inadequate situation
Figure 18 (a) is the operation sectional view of another manufacture method of expression ultrasonic transmitter-receiver shown in Figure 12 to Figure 18 (d).
Figure 19 (a) and Figure 19 (b) are the vertical views of representing other configuration example of protection portion respectively.
Figure 20 is the sectional view of the tenth embodiment of ultrasonic transmitter-receiver of the present invention.
Figure 21 is the vertical view of the tenth embodiment of ultrasonic transmitter-receiver of the present invention.
Figure 22 is the mode chart that ultrasound wave is interfered in the tenth embodiment of expression ultrasonic transmitter-receiver of the present invention.
Figure 23 is the pattern sectional view of hyperacoustic phase place of propagating in protection matching layer and acoustic matching layer.
Figure 24 (a) to (c) is the operation sectional view of manufacture method of the tenth embodiment of expression ultrasonic transmitter-receiver of the present invention.
Figure 25 is that the transmission of the tenth embodiment of ultrasonic transmitter-receiver of the present invention receives oscillogram.
Figure 26 is the sectional view of the 11 embodiment of ultrasonic transmitter-receiver of the present invention.
Figure 27 is that the transmission of the 11 embodiment of ultrasonic transmitter-receiver of the present invention receives oscillogram.
Figure 28 is the sectional view of the 12 embodiment of ultrasonic transmitter-receiver of the present invention.
Figure 29 (a) to (d) is the operation sectional view of manufacture method of the 12 embodiment of expression ultrasonic transmitter-receiver of the present invention.
Figure 30 is the sectional view of the 13 embodiment of ultrasonic transmitter-receiver of the present invention.
It is respectively the vertical view of the 14 embodiment of ultrasonic transmitter-receiver of the present invention that Figure 31 (a) reaches (b).
Figure 32 is the sectional view of the 15 embodiment of ultrasonic transmitter-receiver of the present invention.
Figure 33 is the block scheme of ultrasonic flow meter in expression the 16 embodiment of the present invention.
Figure 34 (a) and Figure 34 (b) are the figure of the waveform measured by ultrasonic flow meter of the present invention of expression.
Figure 35 is a sectional view of representing ultrasonic flow meter always.
Figure 36 is a ultrasonic transmitter-receiver sectional view always.
Embodiment
With reference to the accompanying drawings embodiments of the present invention are described.
(embodiment 1)
Fig. 1 represents a cross section of ultrasonic transmitter-receiver in first embodiment of the present invention (ultrasonic vibration oscillator).Illustrated ultrasonic transmitter-receiver 1 has piezoelectrics 4, the acoustic matching layer 3 that on piezoelectrics 4, is provided with, and for the fixing protection portion 2 of piezoelectrics 4.
Piezoelectrics 4 are made of the material with piezoelectric property, polarize on thickness direction.In the top and bottom of piezoelectrics 4, be provided with not shown electrode, radiate ultrasound wave based on the voltage that electrode is applied.And, having received under hyperacoustic situation, voltage signal takes place between electrode.In the present invention, the material of piezoelectrics 4 is any, also can use the material of knowing altogether.
With interarea (the ultrasound wave transmission receiving plane) S1 of piezoelectrics 4 is the thickness that the height H of the protection portion 2 of benchmark has been stipulated acoustic matching layer 3, and in a preferred form, the height of protection portion 2 equates substantially with the thickness of acoustic matching layer 3.
Fig. 2 be presentation graphs 1 ultrasonic transmitter-receiver 1 above.As can be seen from Figure 2, in the ultrasonic transmitter-receiver 1 of present embodiment, ring protection portion 2 surrounds acoustic matching layer 3, and all of the outer peripheral face of acoustic matching layer 3 (side) contacts with the inner peripheral surface of protection portion 2.By such protection portion 2 is set on piezoelectrics 4, make acoustic matching layer 3 be not easy to peel off from piezoelectrics 4.And, can also prevent the breakage of acoustic matching layer 3.The result significantly improves the fabrication phase of ultrasonic transmitter-receiver 1 and the reliability of operational phase.
Also have, the manufacture method that will narrate according to the back is by adjusting the height H of protection portion 2, the thickness of guide sound matching layer 3 accurately.Like this, because can high precision, stably form acoustic matching layer 3, so can be with the ultrasonic transmitter-receiver of high yield rate quality bills of materials excellence.Because when the thickness of acoustic matching layer 3 with element deviation took place, the characteristic of ultrasonic transmitter-receiver (sensitivity etc.) meeting change was very important so repeatability forms the acoustic matching layer 3 with set thickness well.As previously described, be about and send 1/4 of hyperacoustic wavelength of receiving for obtaining the maximum thickness that sends the suitable acoustic matching layer of receiving sensitivity.Therefore, use the velocity of sound to be about under the situation of the hyperacoustic transmission of the about 500kHz of desiccant gel of 280m/s and reception in acoustic matching layer, the preferred thickness of the acoustic matching layer of desiccant gel is necessary to be set at about 140 μ m.This thickness have about 10% not simultaneously, send receiving sensitivity change about 20% just might take place.Like this, by the subtle change of the thickness of acoustic matching layer 3, sending receiving sensitivity just has big change, but according to present embodiment, can form the acoustic matching layer 3 with desired thickness with good repeatability.
The ultrasonic transmitter-receiver 1 of present embodiment for example can be by following method manufacturing.
At first, prepare to receive the piezoelectrics 4 that hyperacoustic wavelength matches with transmission.As piezoelectrics 4, the high material of piezoelectricity such as piezoelectric ceramics and pressure point monocrystalline preferably.As piezoelectric ceramics, can use lead zirconate titanate, barium titanate, lead titanates, lead niobate etc.And, as piezoelectric monocrystal, can use lead zirconate titanate monocrystalline, lithium niobate, crystal etc.
In the present embodiment, what use as piezoelectrics 4 is the lead zirconate titanate piezoelectric ceramics, sends to receive frequency of ultrasonic and be set at 500kHz.In order to make piezoelectrics 4 high-level efficiency receive such ultrasound wave, so the resonant frequency of element is designed to 500kHz to sending.Therefore, in the present embodiment, the formed piezoelectrics 4 of cylindrical piezoelectric pottery have been used by diameter 12mm, the about 3mm of thickness.
For such piezoelectrics 4, engage the ring protection portion 2 of external diameter 12mm, internal diameter 11mm, thickness 140 μ m.In the present embodiment, as protection portion 2, use be the becket of stainless steel.Stainless protection portion 2 can be undertaken by the bonding of bonding agent with engaging of piezoelectrics 4.For example, use epoxy be resin as bonding agent, when applying the pressure of 0.2MPa, in 150 ℃ calibration cell, placed 2 hours, its sclerosis is got final product.
In the present embodiment, form acoustic matching layer 3 by desiccant gel.Because the velocity of sound of the acoustic matching layer 3 that is formed by desiccant gel is about 280m/s, so hyperacoustic wavelength is about 640 μ m in the acoustic matching layer 3.Therefore, the thickness of setting acoustic matching layer 3 is 140 μ m, equals 1/4 of hyperacoustic wavelength in the acoustic matching layer 3.For the acoustic matching layer 3 that forms this thickness, in the present embodiment, the thickness of setting protection portion 2 is 140 μ m.
The effect of protection portion 2 at first is fabrication phase and the operational phase at ultrasonic transmitter-receiver 1, can protect acoustic matching layer 3 not to be subjected to physical shock or thermal shock from the outside.The second, as the action (use) of ultrasonic transmitter-receiver 1 time, the hyperacoustic vibration that is not sent reception for protection ultrasonic transmitter-receiver 1 also has important effect.
In order to make acoustic matching layer 3 its effects of performance, importantly, make piezoelectrics 4 and acoustic matching layer 3 fluid-tight engagement.Even very small peeling off takes place between piezoelectrics 4 and acoustic matching layer 3, can not bring into play the effect as acoustic matching layer 3.
The present inventor found as shown in Figure 2 in order to keep the fluid-tight engagement of piezoelectrics 4 and acoustic matching layer 3, and the structure that protection portion 2 is set at the peripheral part of acoustic matching layer 3 is is very gone and offered one's services.Under the situation of protection portion 2 not, during the manufacturing of ultrasonic transmitter-receiver 1 and when using etc., its characteristic worsens significantly, has to make the possibility that ultrasonic transmitter-receiver 1 can not practicability.
The acoustic matching layer 3 of present embodiment is that (material that ρ * C) acoustic impedance of defined is very little is constituted by density p and velocity of sound C long-pending.Therefore, can bring up to very high for hyperacoustic transmission receiving efficiency of gases such as air.As the especially little material of acoustic impedance, used above-mentioned desiccant gel in the present embodiment.
By form acoustic matching layer 3 by desiccant gel, with compare by the situation of the formed acoustic matching layers of material always such as resin material fixing glass ball and baton round, because the acoustic matching between the gas piezoelectrics is very good, especially improve so can make ultrasound wave send receiving efficiency.
What is called in this instructions " desiccant gel ", be meant by the formed porous plastid of sol gel reaction, be by solidified solid skeletal portion of reaction institute of gel material liquid,, remove the material that desolvates and form by drying through comprising the moistening gel that solvent constitutes.This desiccant gel is that the solid skeletal portion by nano-scale has formed the nanoporous plastid of average pore diameter approximate number nm to the continuous pore of number μ m.
Since be porous plastid with such microtexture, can the also minimum character of the velocity of sound minimum, that propagate by the part of the gas in the porous body that constitutes by pore simultaneously so have the velocity of sound of propagating by solid portion.Therefore, express the very little value of the following degree of 500m/s, can access and always the diverse low acoustic impedance of acoustic matching layer as the velocity of sound.And in nanometer sized pores portion, under the situation about using as acoustic matching layer in order to increase the gaseous tension loss, also having can be with the feature of high acoustic pressure radiation sound wave.
As the material of such desiccant gel, can use various materials such as inorganic material, high-molecular organic material.Solid skeletal portion as inorganic material can use monox, aluminium oxide, titanium dioxide etc.And the solid skeletal portion as high-molecular organic material can use general thermoset resin, thermoplastic resin etc., for example, can use polyurethane, polyureas, phenol hardening resin, polyacrylamide, polymethylmethacrylate etc.
In the present embodiment, form acoustic matching layer 3 in the inside of piezoelectrics 4 and the 2 formed matrix space P1 (with reference to Fig. 1) of protection portion by above-mentioned desiccant gel in advance.That is to say, after liquid gel material liquid flows into by piezoelectrics 4 and the 2 formed matrix space P1 of protection portion,, form desiccant gel as acoustic matching layer 3 by carrying out gelation, hydrophobization and drying.Also have, in the present embodiment, the desiccant gel that has used the solid skeletal with monox is as acoustic matching layer 3.
Particularly, by carrying out operation shown below 1～4 in the following order, can form acoustic matching layer 3.
1. prepare gel material liquid (colloidal sol) with tetraethoxysilane, ethanol and ammonia spirit (regulation 0.1) 1:3:4 modulation in molar ratio.
2. with dropper this gel material liquid is splashed into by the formed matrix of piezoelectrics and protection portion space.At this moment, the gel material liquid more excessive that drip than matrix space P1 volume.Then, carry out rupturing operation, make the height of the gel material liquid that is retained in the P1 of matrix space identical, afterwards, cover by special teflon plate with the height H of protection portion by the flat board (not shown) that uses special teflon (registered trademark) system.
3. placed about one day in room temperature, in material liquid gelation (forming moistening gel) afterwards, take off special teflon plate.Thereafter, carrying out hydrophobization in trimethylethoxysilane is the hexane solution of 5wt% handles.
4. import the supercritical drying groove, under the condition of 50 ℃ of carbon dioxide atmospheres, pressure 12MPa, temperature, carry out supercritical drying.Like this, form desiccant gel.
By 1～4 above operation, for example, can form density p is 0.3 * 10 3Kg/m 3, velocity of sound C is 280m/s, thickness is the acoustic matching layer 3 of 140 μ m.
The present invention is being 50kg/m by density 3Above 1000kg/m 3Below, and acoustic impedance is 2.5 * 10 3Kg/m 2/ s above 1.0 * 10 6Kg/m 2Its effect can be brought into play significantly under the situation of the acoustic matching layer that material forms that/s is following,, such acoustic matching layer can be successfully produced according to said method.
According to said method because the thickness of acoustic matching layer 3 is equated substantially with the height H of protection portion 2, so can be by protection portion 2 thickness of guide sound matching layer 3 accurately.Protection portion 2 can also say the guide function with gel material liquid in some stage of manufacturing process.
According to said method, owing to can form the little acoustic matching layer 3 of thickness deviation with high yield rate, so can suppress the deviation of the characteristic of ultrasonic transmitter-receiver.Also have, in the present invention, the height of protection portion 2 equates also not to be indispensable with the thickness of acoustic matching layer 3.Under the big situation of the thickness of the aspect ratio acoustic matching layer 3 of protection portion 2, can suppress the contraction of acoustic matching layer 3, give full play to the function that protection is not subjected to physical shock.Otherwise, under the little situation of the thickness of the aspect ratio acoustic matching layer 3 of protection portion 2, compare with the situation that protection portion 2 is not set, also can suppress the contraction of acoustic matching layer 3, highly the performance protection is not subjected to the function of physical shock.
About being provided with the ultrasonic transmitter-receiver of the acoustic matching layer of making by said method 4, it being sent the reception waveform measure.Be shown in Fig. 3 (a) by measuring resulting oscillogram.In order to compare, the transmission reception oscillogram that will be used in by the material of epoxy resin cure glass bead under the acoustic matching layer situation is shown in Fig. 3 (b).Here the acoustic matching layer of employed glass bead, density is 0.52g/cm 3, the velocity of sound is 2500m/s, thickness is 1.25mm.
Also have, as described in the prior art, the acoustic impedance of preferred acoustic matching layer is expressed the value of formula (5) defined.In the present embodiment, use the lead zirconate titanate piezoelectric ceramics in piezoelectrics 4, setting air is as the propagation medium of propagate ultrasound waves.So, because the density of piezoelectrics 4 is 7.7 * 10 3Kg/m 3, the velocity of sound is 3800m/s, so acoustic impedance is about 29 * 10 6Kg/m 2/ s.On the other hand, because the density of air is 0.00118kg/m 3, the velocity of sound is 340m/s, so its acoustic impedance is about 0.0004 * 10 6Kg/m 2/ s.Therefore, according to formula (5), the preferred acoustic impedance of acoustic matching layer is about 0.1 * 10 in theory 6Kg/m 2/ s.
The acoustic impedance of acoustic matching layer 3 in the ultrasonic transmitter-receiver 1 of present embodiment is because density is 0.3 * 10 3Kg/m 3, the velocity of sound is 280m/s, so its acoustic impedance value is about 0.084 * 10 6Kg/m 2/ s, very approaching with theoretic ideal value.
As shown in Figure 3, according to present embodiment, compare the sensitivity that can access more than 3 times with sensor always.And; in the present embodiment; owing to be provided with protective seam 2; so even physical strength is low by having, the ultrasonic transmitter-receiver of the formed acoustic matching layer of desiccant gel of easy damage; also can be with high yield rate manufacturing; and in use, also can carry out the work of long-time high reliability.External vibration test, thermal shock test have been carried out, continuous shaking test etc., under exacting terms, whether acoustic matching layer 3 peeled off from piezoelectrics 4 and estimate, confirmed that the performance of ultrasonic transmitter-receiver does not worsen, can carry out very stable work.
In the present embodiment, in above-mentioned operation 4, when dry moistening gel obtains desiccant gel,, also can in common atmosphere, carry out drying though use is supercritical drying.In this case, shrinking to the process that desiccant gel changes from moistening gel, 10～20% volume change can take place.When such volumetric contraction took place, in structure always, acoustic matching layer 3 will be peeled off from piezoelectrics 4.But under the situation of present embodiment, owing to have protection portion 2 as shown in Figure 4, so the contraction of desiccant gel mainly is only to take place on thickness direction.That is to say that on the interface of piezoelectrics 4 and acoustic matching layer 3, the stress of direction in the generating plane hardly is so have the effect that prevents that acoustic matching layer 3 from peeling off.So,, also can make the ultrasonic transmitter-receiver 1 of high sensitivity, high reliability, and can lower manufacturing cost even adopt the air drying method easier than supercritical drying.
Also have, consider the shrinkage factor of desiccant gel, preferably the thickness setting with protection portion 2 must make the thickness of final acoustic matching layer 3 have best size.Also have, the degree of contraction is excessive, and the thickness of the thinnest part of acoustic matching layer 3 reduces to 90% when following of average thickness, and the characteristic degradation of acoustic matching layer 3 is so be unfavorable.By supercritical drying, the thickness of thin part of acoustic matching layer 3 can be maintained more than 98% of average thickness.
For with above the piezoelectrics that join below 4 of acoustic matching layer 3, and the medial surface of the protection portion 2 of joining with the side of acoustic matching layer 3, preferably carry out surface treatments such as plasma clean and acid treatment in advance.Form hydroxyl by such processing at surface of contact, can make between desiccant gel and piezoelectrics 4 and the protection portion 2 strong by chemical bond.
In order to realize strong combination the between acoustic matching layer 3 and piezoelectrics 4 and the protection portion 2, the asperities processing is carried out in the zone that can combine with acoustic matching layer 3 in the surface of piezoelectrics 4 and protection portion 2.As the method for asperitiesization, can effectively utilize the methods such as corrosion operation of common file, blasting treatment, physics or chemistry.
In order to improve the fluid-tight engagement of acoustic matching layer 3 and protection portion 2, using porous material also is effective as the material of protection portion 2.By forming protection portion 2 by porous material, integrated owing to can make the part of acoustic matching layer 3 be impregnated into the inside of protection portion 2, so can access more strong engagement state.
As the porous plastid that in protection portion 2, may use, can list the metal made by foaming etc., pottery, resin etc.As porous matter metal, can use stainless steel, nickel, copper etc., can use aluminium oxide, barium titanate etc. as pottery, can use various materials such as epoxy resin, urethane as resin.
Also have, in this manual, " protection acoustic matching layer " is not only the protection acoustic matching layer and is not subjected to mechanical vibration and impact etc., but also is included in peeling off of inhibition acoustic matching layer in the operation of the material acoustic matching layer that shrinks when forming.By adopting the guard block of such protection acoustic matching layer; even by a little less than the physical strength, have inotropic material and form acoustic matching layer, the function of acoustic matching layer (coupling by sound makes the hyperacoustic transmission between piezoelectrics and the hyperacoustic propagation medium receive the function that can carry out expeditiously) also can continue practical level.
(second embodiment)
With reference to Fig. 5 second embodiment of the present invention is illustrated.In the present embodiment, protection portion and piezoelectrics are integrated.Particularly, at the interarea central portion formation recess 5a of piezoelectrics 5, a part of 5b of piezoelectrics 5 uses as protection portion.In other words, a part of 5b of piezoelectrics 5 has the function as protection portion, and protection portion and piezoelectrics are integrally formed.
The ultrasonic transmitter-receiver of Fig. 5 is to be made by following method.
At first, after having prepared to have done the piezoelectrics 5 that polarization handles, face (interarea) processing to a side of piezoelectrics 5 forms recess 5a.For forming the processing of recess 5a, can be undertaken by slotting cutter and sand-blast device.The degree of depth of recess 5a is corresponding with the height of protection portion (5b)., on the face that formed recess 5a form electrode, also form electrode at the face opposite with the recess of piezoelectrics thereafter.Electrode for example can be formed metal films such as gold, nickel by methods such as plating, sputters and make.
According to present embodiment,, do not need the protection portion of making in addition to be engaged in the operation of piezoelectrics owing to, make the periphery of its interarea have the function of protection portion to piezoelectrics 5 processing.In the joint of protection portion, use under the situation of bonding agent; must consider the variation of the protective seam height that the existence owing to adhesive linkage causes; but according to present embodiment; owing to can regulate the thickness of acoustic matching layer 3 accurately by the protection portion of high precision specified altitude, so stable, high performance ultrasonic transmitter-receiver can be provided.
In the present embodiment, also preferably carry out the processing that forms hydroxyl for the part that contacts with acoustic matching layer 3 in the surface of piezoelectrics 5.And, in the man-hour that adds of carrying out forming recess 5a,, can also further improve the fluid-tight engagement of acoustic matching layer 3 and piezoelectrics 5 if piezoelectrics 5 are carried out the asperities processing at piezoelectrics 5.
In above-mentioned first embodiment and second embodiment,, be to form the ring-type have with the perpendicular side of interarea of piezoelectrics 5 as the part of protection portion function.But the side of this protection portion also can have as shown in Figure 6 coniform.And as shown in Figure 7, whole the contacting that there is no need with the circumferential lateral surface of acoustic matching layer 3 also can be to have the structure that is divided into a plurality of parts, and a part forms the structure of breach etc.
According to above-mentioned first embodiment or second embodiment; even in acoustic matching layer, use under the situation of the material that the desiccant gel isodensity is low, the velocity of sound is little; protection portion also can strong acoustic matching layer and the combining of piezoelectrics; bring into play high transmission receiving sensitivity; make simultaneously to send the processing in manufacturing process's stage of oscillator at ultrasound wave and become easily, high performance ultrasound wave transmission oscillator can be provided with high yield rate.And, can also be implemented in operational phase that ultrasound wave sends oscillator and be not easy to cause element characteristic degradation, the reliability excellence because of mechanical vibration and the vibration of following hyperacoustic transmission to receive.
(the 3rd embodiment)
With reference to Fig. 8 the 3rd embodiment of the present invention is illustrated.
The unique point of present embodiment is to have structural support 6.Supporter 6 shown in Figure 8 is provided with the discoideus support portion 6a of fixed sound matching layer 3 grades, with from this discoideus support portion to the cylindrical portion 6b that axially extends continuously.The end cross-sectional of cylindrical portion is bent into " L " type, so that can easily be fixed on the plate 60 that is used to cover and other device.
On the surface of the support portion of structural support 6 6a, dispose acoustic matching layer 3 and protection portion 2, dispose piezoelectrics 4 at the back side of support portion 6a.That is to say that piezoelectrics 4 and acoustic matching layer 3 are separately positioned on clamp structure supporter 6 and relative position.By using such structural support 6, manipulating of ultrasonic transmitter-receiver is just very easy.
Structural support 6 can be made of sealable container (Sensor box).In this case,, and be full of inert gas in the structural support 6, then the fluid of piezoelectrics 4 with the measurement of rate of flow object can be cut off if the open end of the cylindrical portion 6b of structural support 6 uses plate 60 to be stopped up by covering.In order to apply voltage,, the danger that puts on inflammable gas is arranged then if center on piezoelectrics 4 with inflammable gas to piezoelectrics 4.But,,, can prevent such igniting, so, also can radiate ultrasound wave safely even for inflammable gas by inside is cut off with outside because structural support 6 is made of the leakproofness container.And, even outside gas is not flammable, reacting with piezoelectrics 4, may make in the gas of characteristic degradation of piezoelectrics 4 under the hyperacoustic situation of radiation, also can be by the gas of piezoelectrics 4 with the outside is cut off, suppress the deterioration of piezoelectrics 4, can in long-time, realize the high work of reliability.
Also have, in the example of Fig. 8, protection portion 2 is configured in the outer periphery portion of the ultrasound wave transmission receiving plane of piezoelectrics 4.Because the effect of acoustic matching layer 4 can not be played by the portion of protection usually 2, so on the interarea of piezoelectrics 4 during configuration protection portion 2, this part just becomes hyperacoustic transmission is received the part that not have contribution, makes to send the sensitivity decline that receives.
In order to make structural support 6 not become the essential factor of obstruction sound, the thickness of the discoideus support portion 6a of preferred piezoelectrics 4 contacts receives below 1/8 of ultrasound wave wavelength for sending.By being the about below 1/8 of wavelength with this thickness setting, structural support 6 can not hinder hyperacoustic propagation.
In the present embodiment, be to use the material of stainless steel as structural support 6, the thickness setting of structural support 6 is 0.2mm.Because the velocity of sound in the stainless steel is about 5500m/s, thus 0.2mm be equivalent to frequency be 500kHz the ultrasound wave medium wavelength 1/55.Owing to form structural support 6,, also become the obstacle of sound hardly even structural support 6 is present in hyperacoustic travel path by thin like this stainless steel.
The material of structural support 6 is not limited to metal material, also can select to obtain from pottery, glass, resin etc. according to purpose.In the present embodiment, even also can prevent the intensity that piezoelectrics contact with external fluid, made structural support 6 by metal material in order reliably piezoelectrics to be separated with external fluid and to give that structural support 6 is applied some physical shock.Thus, even, also can guarantee high security for example with flammable and to have volatile gas be that object carries out hyperacoustic transmission and receives.
Under the situation of carrying out hyperacoustic transmission reception for security gas, be purpose to reduce the cost, also can form structural support 6 by materials such as resins.
In order to improve the fluid-tight engagement of structural support 6 and acoustic matching layer 3, preferably in the surface of structural support 6 with acoustic matching layer 3 contacted parts, add the Cement Composite Treated by Plasma of hydroxyl and oxygen processing etc. in advance.And, also can carry out roughening treatment to this part by the methods such as corrosion of file and blasting treatment, chemistry and/or physics.
(the 4th embodiment)
Then, with reference to Fig. 9 the 4th embodiment of the present invention is illustrated.
In the ultrasonic transmitter-receiver of present embodiment, a part of 7a of structural support 7 has the function as protection portion, structural support 7 and protection integrally.For example when making structural support 7 by the pressure processing of stainless steel and other metal materials, form recess 7b on its discoideus support portion, the periphery of recess 7b (the part 7a that is bent by the pressure forming of structural support 7) can use as protection portion.
By adopting such structure, can save the operation that protection portion is engaged in structural support.And, same with first embodiment, owing to the deviation that does not have by the height of the caused protection of tack coat portion, so can make highly sensitive ultrasonic transmitter-receiver with good yield rate.
Also have, in Fig. 9, do not have to record and narrate plate, but as required, such plate also can be engaged in structural support 7 or integrated with it for closed structure supporter 7.Below Shuo Ming other embodiment also is same.
(the 5th embodiment)
With reference to Figure 10 and Figure 11 the 5th embodiment of the present invention is illustrated.
The ultrasonic transmitter-receiver of present embodiment is provided with other acoustic matching layer (lower floor's acoustic matching layer) 8 between acoustic matching layer 3 and piezoelectrics 4.Except the insertion of lower floor's acoustic matching layer 8, the structure of the structure of present embodiment and second embodiment is same.
Acoustic matching layer suppresses the internal reflection by the caused sound wave that do not match of acoustic impedance, plays the effect of expeditiously ultrasound wave being radiated to medium (ultrasonic propagation medium) from piezoelectrics.Such acoustic matching layer under the situation of the ultrasound wave (ultrasound wave of continuous wave) that sends or accept to have single-frequency, has one deck just enough.
In contrast to this, in common ultrasonic transmitter-receiver, be the ultrasound wave that sends received pulse or outburst (burst) shape.The ultrasound wave of pulse or outburst shape is not single frequency content, but comprises wide band frequency range.Receive for such ultrasound wave being carried out highly sensitive transmission, preferably the acoustic impedance of acoustic matching layer can change lentamente between piezoelectrics and ultrasonic propagation medium.For acoustic impedance is changed so lentamente,, the acoustic impedance that constitutes layer is slowly changed get final product the acoustic matching layer multiple stratification.
In the present embodiment, as shown in figure 10, acoustic matching layer is two-layer.Particularly, as lower floor's acoustic matching layer 8, used the porous sintered article that constitutes by pottery.The apparent density of this lower floor's acoustic matching layer 8 about 0.64 * 10 3Kg/m 3, the velocity of sound is 2000m/s, acoustic impedance about 1.28 * 10 6Kg/m 2/ s.As stupalith, use be the material of barium titanate series.
So-called " apparent density " is meant the density that comprises space segment in the porous body.About 80% of its volume of porous ceramic is space segment (hole), and the entity portion of pottery is all about 20vol%.Such porous ceramic is that resinous ball is mixed with ceramic powders, behind the press molding, to the resin balls heating, its burning removal is formed in the sintering process of pottery.If during sintering the heating too rapid since resin balls expand or sharply vaporization ceramic structure is destroyed, so preferably heat slowly.
In the present embodiment, with such lower floor's acoustic matching layer 8 for piezoelectrics 4 (directly being structural support 6) fixing after, in this acoustic matching layer 8, for the face splice protection portion 2 of piezoelectrics 4 opposite sides.Employed protection portion 2 is same in the protection portion 2 and first embodiment, can use the parts by the ring made of stainless steel.Joint can all be undertaken by the cementing agent of epoxy resin.
In like this by lower floor's acoustic matching layer 8 and protection portion 2 formed recesses, same with first embodiment, form desiccant gel layer as acoustic matching layer 3.
In the present embodiment, with the same operation 1 of the operation 1 of first embodiment in, the concentration of the ammonia by changing the gelation reaction catalyzer is adjusted the density of desiccant gel, the density that forms as acoustic matching layer is 0.2 * 10 3Kg/m 3, the velocity of sound is 160m/s, acoustic impedance is about 0.032 * 10 6Kg/m 2The desiccant gel layer of/s.Because the velocity of sound of acoustic matching layer is 160m/s, so the height setting of protection portion 2 is 80 μ m, be in the acoustic matching layer ultrasound wave wavelength 1/4.Preferably can carry out the processing of giving hydroxyl by plasma etching to the medial surface of protection portion 2.
Figure 11 (a) is that the transmission of ultrasonic transmitter-receiver in the expression present embodiment receives waveform.In the figure of Figure 11, ordinate is a signal amplitude, and horizontal ordinate is the time.Numerical value on the coordinate axis is the index mark, and for example " 2.0E0-4 " implication is 2.0 * 10 -4Also be same among other the figure.
In measuring employed ultrasonic transmitter-receiver, setting is 1mm as the thickness of the porous ceramic of lower floor's acoustic matching layer 8, and the thickness of the protection portion 2 and first acoustic matching layer (desiccant gel layer) 2 is 80 μ m.
In order to compare, in the ultrasonic transmitter-receiver of Figure 10, use acoustic matching layer always to replace two-layer acoustic matching layer 3,8 and make ultrasonic transmitter-receiver by the epoxy resin cure glass bead, this ultrasound wave is sent the reception waveform measure.Measurement result is shown in Figure 11 (b).
Two-layer by acoustic matching layer is made as, compare with ultrasonic sensor always, obtained about 20 times high sensitivity.And, even compare,, also realized broad in band (short pulseization) realizing the highly sensitive while with the ultrasonic sensor of first embodiment.Like this, by two stratification of acoustic matching layer, can provide the ultrasonic transmitter-receiver that is very suitable for sending received pulse and outburst ripple.
(the 6th embodiment)
With reference to Figure 12 the 6th embodiment of the present invention is illustrated.
In the present embodiment, the part of the acoustic matching layer 9 of lower floor has the function of protection portion, acoustic matching layer 9 and protection integrally.In this embodiment, to acoustic matching layer 9 processing, on its interarea, form recess.Become the desiccant gel layer of the acoustic matching layer 3 on upper strata, in the recess of the acoustic matching layer 9 of lower floor, form.
By adopting such structure, can save the operation that protection portion is engaged in acoustic matching layer 9.And, also can be resolved by the problem of the caused protection of tack coat portion height tolerance, so can be manufactured on the ultrasonic transmitter-receiver of high sensitivity work in the wide frequency band range with high yield rate.
In the present embodiment, the acoustic matching layer 9 of lower floor is formed by porous plastid.Therefore, strong with combining of the acoustic matching layer 3 on upper strata, can guarantee high sensitivity, and high stability.In order further to improve this fluid-tight engagement, preferred Cement Composite Treated by Plasma or acid treatment of giving hydroxyl to the acoustic matching layer 3 on upper strata and the surface of contact of the acoustic matching layer 9 of lower floor in advance.
In present embodiment and described the 5th embodiment, acoustic matching layer all has two-layer structure, but ultrasonic oscillator of the present invention is not limited to such structure, also can have the sandwich construction more than three layers.By the multiple stratification of acoustic matching layer, can further improve sensitivity, enlarge frequency band.But owing in order to improve sensitivity by multiple stratification, must form by the extremely low material of acoustic impedance and form outermost acoustic matching layer, the two-layer structure of practical upward employing is real.
(the 7th embodiment)
Be illustrated with reference to Figure 13～15 pair the 7th embodiment of the present invention.
As shown in figure 13, the ultrasonic transmitter-receiver of present embodiment engages in the rear side of piezoelectrics 4 back side load parts 10, and load the overleaf top of parts 10 of protection portion 2 forms.Others all have identical structure with the 3rd embodiment.
Load parts 10 in the back side have that subtracting declines is sidelong hyperacoustic function of penetrating from piezoelectrics 4 to the back side, if can bring into play such materials with function, by which type of material being formed can.
Protection portion 2 is formed, is engaged with the interarea of back side load parts 10 by the tubular metal.The aggregate thickness of the acoustic matching layer 8 of the thickness of protection portion 2 and piezoelectrics 4, lower floor and the acoustic matching layer 3 on upper strata equates.In the present embodiment, be that the thickness of 1mm, acoustic matching layer 3 is 0.08mm because the thickness setting of piezoelectrics 4 is the thickness of 3mm, acoustic matching layer 8, so the thickness of protection portion 2 is 4.08mm.
The back side of present embodiment load parts 10 are made of ferrite rubber, and ferrite rubber is the material that is dispersed with iron powder in rubber, sound wave subtract the rate height that declines.By such back side load parts 10 being engaged in the back side of piezoelectrics 4, can subtract the ultrasound wave that declines and radiate from the rear side of piezoelectrics 4, can send and receive wide band (pulse width is short) ultrasound wave.
Figure 14 is that the transmission that expression is measured the ultrasonic transmitter-receiver with Figure 13 structure receives waveform.Compare with the ultrasonic transmitter-receiver of the 3rd embodiment, though the transmission receiving sensitivity of the ultrasonic transmitter-receiver of present embodiment has reduction, but can be implemented in the work of wideer frequency band, can constitute the ultrasonic transmitter-receiver that is suitable for short width-pulse transmission reception.
Can also use back side load parts 11 shown in Figure 15 to replace back side load parts 10 shown in Figure 13.Back side load parts 11 shown in Figure 15, its part has the function as protection portion, and protection portion and back side load parts are integrated.Load parts 11 in the back side have the structure that forms recess in the zone except the periphery of interarea, and piezoelectrics 4 are inserted in the recess, engage with the recess inner face of back side load parts 11.Be arranged at the concave depth of back side load parts 11, set greatlyyer,, just obtain the structure of Figure 15 if formation is as the desiccant gel layer of acoustic matching layer above the piezoelectrics after insertion 4 than the height of piezoelectrics 4.Employing by back side load parts 11 can reach the broad in band same with the ultrasonic transmitter-receiver of Figure 13.
(the 8th embodiment)
With reference to Figure 16 the 8th embodiment of the present invention shown in Figure 12 is illustrated.
At first, shown in Figure 16 (a), piezoelectrics 4 are engaged in structural support 6 with lower floor's acoustic matching layer 9.Can use cementing agent in the joint.As previously mentioned, piezoelectrics 4 are formed by piezoelectric ceramics, and structural support 6 is formed by stainless steel.Lower floor's acoustic matching layer 9 is formed by top porous ceramics with recess.This recess is to the top processing of flat porous ceramic and form by lathe.
Then, shown in Figure 16 (b), form desiccant gel as the upper strata acoustic matching layer for the recess of lower floor's acoustic matching layer 9 of the state that is engaged in structural support 6.The formation of desiccant gel can be undertaken by the method that illustrates in first embodiment.
Fully to soak into the gel raw material in order making in the acoustic matching layer 9 that forms by porous ceramics, preferably after the gel raw material flows into, to be disposed in vacuum or the reduced atmosphere.Like this, in the present embodiment, the gel raw material not only has the funtion part as the protection portion of acoustic matching layer 9, but also it is all to soak into the inside of acoustic matching layer 9.By doing like this, desiccant gel is engaged securely, with lower floor acoustic matching layer 9 so the characteristic that can make acoustic matching layer 9 evenly (Figure 16 (c)).Below, with reference to Figure 17 this point is illustrated.
Figure 17 (a) is illustrated in the state that the gel raw material fully soaks in lower floor's acoustic matching layer 9.For this reason, lower floor's acoustic matching layer 9 has the function as single sound layer, and acoustic impedance from the high relatively value of acoustic matching layer 9, reduces to the low relatively value of the acoustic matching layer on upper strata step-likely.
On the other hand, under the inadequate situation of soaking into of gel raw material, shown in Figure 17 (b), in fact formed the acoustic matching layer of three-decker.In this case, because the acoustic impedance of soaking into inadequate orlop (ground floor) of gel raw material is littler than setting value, so the acoustic impedance of middle layer (second layer) is just maximum.When the distribution of acoustic impedance is shown in Figure 17 (b), from the configuration in the drawings the below piezoelectrics (not shown) to the gas that becomes the ultrasonic propagation medium, acoustic impedance is not step-like diminishing just, can cause the characteristic degradation of ultrasonic transmitter-receiver, so preferably fully carry out soaking into of gel raw material.
In the above-described embodiment, as shown in figure 16, after lower floor's acoustic matching layer 9 is fixed in the operation of structural support 6, form the operation of first acoustic matching layer 3.But the order of these operations also can be opposite.With reference to Figure 18 (a)～(d), other manufacture method is illustrated.
At first, shown in Figure 18 (a), prepare to have acoustic matching layer 9 as protection portion funtion part.Then, shown in Figure 18 (b), in the recess of acoustic matching layer 9, splash into the gel raw material and put down completely, make the height of recess inner gel raw material consistent, gel rubber material is impregnated into all of acoustic matching layer 9 with the height of protection portion.After the sclerosis of gel rubber material, hydrophobization, by supercritical drying the gel raw material is carried out drying, shown in Figure 18 (c), on the acoustic matching layer 9 of lower floor, form acoustic matching layer 3 by desiccant gel constituted.
As Figure 18 (d) shown in, on the structural support 6 that be fixed with piezoelectrics 4 states engage acoustic matching layer thereafter.Also have, also utilization structure supporter 6 not, and the acoustic matching layer of Figure 18 (c) directly is engaged in piezoelectrics 4.
Also have, when engaging,, preferably select best pressurized conditions in order not destroyed because of pressurization makes desiccant gel.Because the intensity for the stress of the compression direction of desiccant gel is higher, so almost there is not the decline of fabrication yield in above-mentioned joint operation.
Also have, the material of preferably selected acoustic matching layer 3 and acoustic matching layer 9 makes the elastic modulus of the acoustic matching layer 9 of the elastic modulus of acoustic matching layer 3 on upper strata and lower floor show approaching value mutually.The elastic modulus of the two near the time, can for the composition surface all give uniform pressure, make highly sensitive ultrasonic transmitter-receiver with high finished product rate easily.
In the method shown in Figure 18 (a)～(d), on acoustic matching layer 9, form in the operation of desiccant gel, owing to there is no need piezoelectrics and structural support etc. are disposed,, can make ultrasonic transmitter-receiver with low cost so can make device miniaturization such as drying device.
In the formation operation of desiccant gel,,, the bonding part is not worsened by engaging operation after forming at desiccant gel though there is organism such as pair tack coat to apply the possibility of chemistry load.
(the 9th embodiment)
With reference to Figure 19 other embodiment of the present invention is illustrated.
The unique point of present embodiment is that protection portion 2 not only forms at the peripheral part in the zone that has formed acoustic matching layer 3, and also forms at this intra-zone.
From the gel raw material when moistening gel forms the desiccant gel layer, the concavo-convex situation of formation on the desiccant gel layer is arranged.And, moistening gel is not carried out under the dry situation by common drying means not using supercritical drying, because the contraction of desiccant gel takes place, on desiccant gel, form recess as shown in Figure 4 easily.
Send to receive under the wide situation in corrugated at ultrasound wave, above-mentioned concavo-convex easy change is big, even be optimum value with the thickness setting of acoustic matching layer, in fact according to the place etc., the thickness of acoustic matching layer can big change take place from optimum value.
Because it is the velocity of sound is very little in the desiccant gel layer, in order to have the appropriate functional as acoustic matching layer, need form as thin as a wafer, also little to the scope of the permissible error of thickness.
If formed the protection portion with the layout shown in Figure 19 (a) or Figure 19 (b), then the error of acoustic matching layer thickness can be suppressed in pact ± 5% of desired value.
Shown in Figure 19 (a) or Figure 19 (b); if the inside at the ultrasonic wave radiation face of ultrasonic transmitter-receiver also is provided with protection portion 2; though the thickness variation of acoustic matching layer 3 can be suppressed to minimum, the protection portion 2 that is arranged on the inboard of ultrasonic wave radiation face can become the obstruction essential factor that sends reception for ultrasound wave.For the deterioration of the sound characteristics that prevents to cause,, in the scope that can bring into play as the effect of protection portion 2, reduce as best one can preferably with the size of protection portion 2 by protection portion 2.
In the configuration example of Figure 19 (a), be that the random arrangement cross section is circular protection portion 2, but the cross section of protection portion 2 is not limited to circle, also can be rectangle and polygon etc.And configuration also is not limited at random.
In the configuration example of Figure 19 (b), be to be provided with concentric two circular protection portions 2.In this configuration example, also there is protection portion 2 in the inside of the ultrasonic wave radiation face of ultrasonic transmitter-receiver, can prevent the characteristic degradation of ultrasonic transmitter-receiver.The structure of Figure 19 (b) is for being effective from ultrasonic wave radiation towards only leaving closely that the position of L sends under hyperacoustic situation on the central shaft of ultrasonic transmitter-receiver.
When if the distance between the center of protection portion 2 and ultrasonic wave radiation face is r, preferred distance r can satisfy following formula (6).
n 2 &lambda; 2 4 + n&lambda;L &le; r &le; ( n + 1 ) 2 &lambda; 2 4 + ( n + 1 ) &lambda;L ( n = 1,3,5,7 &CenterDot; &CenterDot; &CenterDot; ) - - - ( 6 )
In the formula, λ is the wavelength of ultrasound wave in propagating gas, and L is the distance from the ultrasonic wave radiation face of ultrasonic transmitter-receiver.For example; in frequency is 50kHz, and the ultrasonic propagation medium is air (velocity of sound 340m/s), and measuring distance is under the situation of 10mm; by formula (6) as can be known, be 2.6～3.7mm, 4.6～5.4mm, 6.1～6.7mm preferably in the radius r of distance center ... the position protection portion 2 is set.In these positions protection portion 2 is set, can prevents that it is effective worsening for the sensitivity that prevents ultrasonic proximity by the disorder of caused of the interference of sound.
The each point of the sound wave emitting surface of ultrasonic transmitter-receiver is considered as point sound source respectively, then synthesizes the ultrasound wave of transmission by the spherical wave that each point sound source radiated.Under the near situation of distance ultrasonic wave radiation face, because the different ultrasound wave of phase place can offset, so have the position that can not send high output ultrasonic wave.In order only to radiate the identical ultrasound wave of phase place from the ultrasonic wave radiation face, it is effective in the different hyperacoustic zone of radiation phase place protection portion 2 being set.In such zone protection portion 2 is set, owing to can suppress the different hyperacoustic radiation of phase place, so can prevent the closely disorder of sound field, the ultrasound wave that can carry out high output sends.
(the tenth embodiment)
Figure 20 is the sectional view of the tenth embodiment of ultrasonic transmitter-receiver of the present invention.The ultrasonic transmitter-receiver 21 of present embodiment; be provided with piezoelectrics 22; the electrode 23a, the 23b that are provided with on the two sides of piezoelectrics 22; the protection matching layer that on piezoelectrics 22, is provided with (first acoustic matching layer) 4, and the acoustic matching layer that on piezoelectrics 22, is provided with (second sound matching layer) 25 by electrode 23a by electrode 23a.
Figure 21 is the vertical view of ultrasonic transmitter-receiver 21 shown in Figure 20.As shown in Figure 21, the ultrasonic transmitter-receiver of present embodiment has the structure that different protection matching layer of thickness (highly) 24 and acoustic matching layer 25 are configured to concentric circles alternately.
Piezoelectrics 22 in the present embodiment are made of the material with piezoelectricity, polarize on thickness direction.If electrode 23a, the 23b that is arranged at piezoelectrics 22 top and bottom applied voltage, in piezoelectrics 22, produce ultrasound wave based on voltage signal, radiate to ultrasonic propagation medium (gas etc.) 26 by protection matching layer 24 and acoustic matching layer 25.And, propagate into the ultrasound wave of sonic propagation medium 26, propagate to piezoelectrics 22 by protection matching layer 24 and acoustic matching layer 25.Make piezoelectrics 22 distortion by the incident ultrasound wave, between electrode 23a and electrode 23b, voltage signal takes place.
The material of piezoelectrics 22 is arbitrarily, can use the piezoelectrics of being known altogether by various that material constituted.Can also use the electric response body of knowing altogether to replace piezoelectrics 22. Preferred electrode 23a, 23b are formed by metal, but are made of the conductive material beyond the metal.
The ultrasonic vibration that protection matching layer 24 and acoustic matching layer 25 can piezoelectrics 22 be taken place is propagated to sonic propagation medium 26 expeditiously, and, also have the function that the ultrasonic high-efficiency rate ground that propagates into sonic propagation medium 26 is propagated to piezoelectrics 22.
The acoustic matching layer 25 of preferred present embodiment is formed by desiccant gel.Desiccant gel is by the formed porous plastid of sol gel reaction, is the product (material that ρ * C) acoustic impedance of defined can be minimum by density p and velocity of sound C.Therefore, by using, can make for hyperacoustic transmission receiving efficiency of gases such as air high by the formed acoustic matching layer 25 of desiccant gel.
Desiccant gel is after forming moistening gel, and drying obtains by this moistening gel is carried out.Moistening gel is at first to prepare the gel material liquid, can make moistening gel by the reaction of this gel material liquid.Moistening gel has the cured solid skeleton portion by the reaction of gel material liquid, and this solid skeletal portion is the state that contains solvent.
The desiccant gel that is obtained by moistening Drying of gels is a porous plastid, has the continuous pore of several nm～number μ m in the gap of solid skeletal portion.The average-size of pore is minimum, is 1nm～number μ m.
When the adjusting manufacturing conditions reduced the density of desiccant gel, it is minimum that the velocity of sound of the solid portion of desiccant gel also becomes, and the velocity of sound of gas part is also minimum in the pore simultaneously.Therefore, under the low-density state, the velocity of sound of desiccant gel shows the following low value of 500m/s, expresses extremely low acoustic impedance.Particularly have the undersized solid skeletal portion of several nm and the desiccant gel of fine pore, demonstrate the lower velocity of sound.And, because the pressure loss of gas is big in the nanometer sized pores portion, thus forming by desiccant gel under the situation of acoustic matching layer, can be with high acoustic pressure radiation sound wave.
According to manufacture method described later,,, also can be in wide scope the acoustic impedance of desiccant gel be controlled to be value arbitrarily by regulating process conditions even use same raw material.And by changing fabrication process condition, it is identical substantially to make density, only the acoustic matching layer of sonic velocity change.
Though desiccant gel has such favorable characteristics, its physical strength is low.Therefore, the yield rate that improves when making is just difficult, and the reliability during use is not high yet.By the parts that the low desiccant gel of such physical strength is protected are set, can improve the yield rate and the reliability of manufacturing, these have given explanation in first to the 9th embodiment.
The protection portion of first to the 9th embodiment; for the fabrication yield that improves ultrasonic transmitter-receiver; or the reliability that improves when using all is very effective; and then; owing to can carry out high-precision control, so also be effective for the stable performanceization of ultrasonic transmitter-receiver to the thickness of acoustic matching layer.But, as mentioned above, sending or receive on hyperacoustic (interarea) at piezoelectrics protection portion is set, this protection portion can become the obstacle of sound.And; this be because; in first to the 9th embodiment; to must equate substantially with the thickness of acoustic matching layer by the thickness setting of the formed upper strata of the material that is different from acoustic matching layer material protection portion; so protection portion is different with the velocity of sound between the acoustic matching layer, can not bring into play the effect of acoustic matching layer with the protection portion that the thickness of acoustic matching layer equates substantially.Therefore, in order not become hyperacoustic transmission is received the essential factor that constitutes obstruction, the protection portion of preferred first to the 9th embodiment is configured in the outside of piezoelectrics interarea.
But, because in order to ensure for the reliability of severe rugged environment condition more, and the restriction of ultrasonic transmitter-receiver external diameter etc., the situation of having to be provided with protection portion on the top of piezoelectrics is also arranged.
In the present embodiment; adopted the protection portion (, physical strength high relatively by density constituted than acoustic matching layer 25 high materials) of the function that on the interarea of piezoelectrics, has had protection acoustic matching layer 25; simultaneously, do not damage structure as the ultrasonic transmitter-receiver function.
In the present embodiment, the thickness setting that is arranged at the protection portion on piezoelectrics 22 interareas is accepted about 1/4 of ultrasound wave wavelength for sending.Thus, the protection portion that physical strength is high relatively also can have the function as acoustic matching layer.Therefore, in some cases such protection portion is called " protection matching layer " at this instructions.By adopting such structure, because the effect of acoustic matching layer also can be played by the protection portion of protection acoustic matching layer, so can realize highly sensitive ultrasonic transmitter-receiver.
The thickness of bringing into play best as the effect of acoustic matching layer is 1/4 of ultrasound wave wavelength.On the other hand, the velocity of sound of protection in the matching layer 24 is different with the velocity of sound in the acoustic matching layer 25.Therefore, the protection thickness L3 of matching layer 24 and the thickness L1 of acoustic matching layer 25 as shown in figure 20, have different size (L3〉L1).
Be about 1/4 of the velocity of sound if will protect the thickness of the thickness of matching layer 24 and acoustic matching layer 25 all to be provided with; because the thickness of protection matching layer 24 and the thickness difference of acoustic matching layer 25, so the situation that just has ultrasound wave that above protection matching layer 25, is radiated and the ultrasound wave that above protection matching layer 24, is radiated to interfere.In order to realize highly sensitive ultrasonic transmitter-receiver, Fang She hyperacoustic phase relation is very important separately.
Figure 22 (a) is top hyperacoustic waveform of expression protection matching layer 24, and Figure 22 (b) is the top that is illustrated in protection matching layer 25, with hyperacoustic waveform of the top same level of protecting matching layer 24.Also have, the symbol " ta " among Figure 22 (b) is the time of expression ultrasound wave in 26 propagation of sonic propagation medium.When frequency of ultrasonic was 500kHz, horizontal ordinate scale was about 3 μ s among each figure.
The ultrasound wave that is radiated above acoustic matching layer 25 by ultrasonic propagation media 26 such as gases, arrives the top identical level with protection matching layer 24.Therefore, above acoustic matching layer 25, change with the size L2 of the velocity of sound in the propagation medium 26 and propagation medium 26 with the phase relation of the ultrasound wave waveform of the top identical level of protection matching layer 24.
Also have, Figure 22 (a) and (b) in signal waveform, be to equate and the result that obtains from protection matching layer 24 and hyperacoustic wavelength that acoustic matching layer 25 radiated and amplitude in supposition.
The thickness L1 of protection thickness L3 of matching layer 24 and acoustic matching layer 25 is respectively 1/4 o'clock of ultrasound wave wavelength in each layer, ultrasound wave below protection matching layer 24 with top between propagate the needed time with below acoustic matching layer 25 with top between the needed time of propagation equate.So the ultrasound wave that radiated above acoustic matching layer 25 arrives the hyperacoustic phase place with same level above the protection matching layer 24, it is slow that the top hyperacoustic phase place that arrives protection matching layer 24 with propagating overprotection matching layer 24 is compared.It is corresponding that the slow and ultrasound wave that is radiated above acoustic matching layer 25 of this phase place has only been propagated time of sonic propagation medium 26 middle distance L2.
If sending and receiving frequency of ultrasonic is f (second -1), then ultrasonic propagation and hyperacoustic needed time of wavelength equidistance are 1/f (second).Ultrasound wave is 1/4f (second) by the protection matching layer 24 needed time t3 of present embodiment.On the other hand, ultrasound wave also is 1/4f (second) by the acoustic matching layer 25 needed time t2 of present embodiment.Here; if ultrasound wave only the needed time of distance by L2 in the sonic propagation medium 26 be t2 (=ta), then can exist with ... time t2 between ultrasound wave that above protection matching layer 24, is radiated and the ultrasound wave that above acoustic matching layer 25, radiated and interfere.Hyperacoustic waveform and sensitivity are changed by this interference.
Figure 22 (c) is to be the ultrasound wave waveform of being observed under the 1/2f situation of (second) at time t2, and Figure 22 (d) is to be the ultrasound wave waveform of being observed under the 1/f situation of (second) at time t2.Reach (d) as can be known from Figure 22 (c), hyperacoustic sensitivity of observation has very big difference because of the value of time t2.Time t2 equals 1/2f when (second), and departing from of phase place is hyperacoustic half-wavelength, and hyperacoustic sensitivity of observation descends.On the other hand, time t2 equals 1/f when (second) and since phase place depart from integral multiple for the wavelength of ultrasonic oscillator, so hyperacoustic sensitivity of observation raises.When the time was the scope of 1/2f～1/f (second), along with t2 is approaching to 1/f (second) from 1/2f (second), hyperacoustic transmission receiving sensitivity rose.
Cross sonic propagation medium 26 from the ultrasonic propagation that acoustic matching layer 25 is radiated; arrive when protecting the top identical level of matching layer 24; regulate the thickness of acoustic matching layer 25 and protection matching layer 24; hyperacoustic phase place that this hyperacoustic phase place is come with propagating overprotection matching layer 24 is unanimous on the whole, and highly sensitive ultrasonic transmitter-receiver can be provided.Also have, in this instructions " phase differential is unanimous on the whole ", mean that hyperacoustic phase differential is below 1/4 of ultrasound wave wavelength, preferred phase differential is the smaller the better.
Figure 23 is illustrated in the pattern sectional view that time t2 is the hyperacoustic phase place under the 1/f situation of (second).In the figure, the hyperacoustic phase place above the protection matching layer 24, consistent with the hyperacoustic phase place with the same level of protection matching layer of acoustic matching layer 25 tops.When producing such phase place unanimity, hyperacoustic transmission receiving sensitivity reaches maximization.Also have, even can not produce under the on all four situation of such phase place, setting departing from hour of phase place, hyperacoustic transmission receiving sensitivity also has sufficient raising than in the past.Preferred departing from of phase place can be adjusted to below 1/4 of ultrasound wave wavelength in the ultrasonic propagation medium, more preferably can be adjusted to below 1/8.
Only from the thickness L3 with the thickness L1 of acoustic matching layer 25 and protection matching layer 24 be controlled at respectively acoustic matching layer 25 and protection matching layer 24 the ultrasound wave wavelength about 1/4; because the L2 size is by (L3-L1) institute's monodrome decision is so can not set arbitrarily t2.Therefore, reach desirable size, be not only thickness, and also must carry out suitable control the velocity of sound in acoustic matching layer 25 and the protection matching layer 24 to acoustic matching layer 25 and protection matching layer 24 in order to make time t2.In embodiment preferred for this invention, be easy to desiccant gel by the control of the velocity of sound and form acoustic matching layer 25.
Then,, the embodiment of the manufacture method of ultrasonic transmitter-receiver in the present embodiment 21 is illustrated to (c) with reference to Figure 24 (a).In the present embodiment, considered that as ultrasonic propagation medium 26 (density is 1.18kg/m to air 3, the velocity of sound is about 340m/s, and acoustic impedance is about 4.0 * 10 2Kg/m 2/ s).
At first, shown in Figure 24 (a), prepare to receive the piezoelectrics 22 that hyperacoustic wavelength matches with transmission.On the piezoelectrics 22 in this stage, the protection matching layer 24 shown in Figure 24 (a) is not set.As piezoelectrics 22, the high material of piezoelectricity such as piezoelectric ceramics and piezoelectric monocrystal preferably.As piezoelectric ceramics, can use lead zirconate titanate, barium titanate, lead titanates, lead niobate etc.And, as piezoelectric monocrystal, can use lead zirconate titanate monocrystalline, lithium niobate, crystal etc.
In the present embodiment, what use as piezoelectrics 22 is the lead zirconate titanate pottery, and sending and receiving hyperacoustic wavelength set is 500kHz.For can sending expeditiously, piezoelectrics 22 receive such ultrasound wave, so the resonant frequency of piezoelectrics 22 is designed to 500kHz.Therefore, in the present embodiment, the formed piezoelectrics 22 of cylindrical piezoelectric pottery have been used by diameter 12mm, the about 3.8mm of thickness.Baking on the two sides of piezoelectrics 22 by silver forms electrode 23a, 23b, implements polarization and handle on this direction.
Then, prepare to have three endless members, shown in Figure 24 (a), be engaged in the interarea of piezoelectrics 22 as the function of protection matching layer 24.At this moment, as shown in figure 21, each center of endless member is consistent with the center of piezoelectrics 22.Have three endless members as the function of protection matching layer 24; it is respectively first endless member of external diameter 12mm, internal diameter 11mm, thickness 1.0mm; external diameter 8mm, internal diameter 7mm, thickness 1.0mm and endless member, and the 3rd endless member of external diameter 4mm, internal diameter 3mm, thickness 1.0mm.
In the protection matching layer 24 of present embodiment, not only can obtain the physical strength height, can protect the function of acoustic matching layer, and can access for the function of bringing into play acoustic matching layer and have lower acoustic impedance.As such material, be to use porous ceramic in the present embodiment.The apparent density of porous ceramic about 0.64 * 10 3Kg/m 3, the velocity of sound is 2000m/s, acoustic impedance about 1.28 * 10 6Kg/m 2/ s.As pottery, use be the material of barium titanate series.Also have so-called " apparent density ", be meant the density that comprises space segment in the porous body.Porous ceramic is that about 80% of volume is the space, and the entity of pottery is all about 20vol%.
As mentioned above, because the velocity of sound of protection in the matching layer 24 is about 2000m/s, so 1/4 thickness of 500kHz medium wavelength is equivalent to 1.0mm.Therefore, will be 1.0mm as the endless member thickness setting of the function of protecting matching layer 24 in the present embodiment.
Employed porous ceramic in the present embodiment is obtained by following making.
At first, resinous small ball is mixed press molding with ceramic powders., pottery carried out sintering thereafter, in this sintering process, the resin balls removal that is heated, burns.If heating is too rapid during sintering since resin balls expands or sharply vaporization ceramic structure is destroyed, so preferably carry out sintering by heating slowly.
In the present embodiment, will be by formed protection matching layer of such porous ceramic 24 and piezoelectrics 22, engage by cementing agent etc.For example, using epoxy as cementing agent is resin, when applying the pressure of 0.1MPa, in 150 ℃ calibration cell, placed about 2 hours, and hardening of resin, protection matching layer 24 engages with piezoelectrics 22.
Then, on the complex that is constituted by the such piezoelectrics that form 22/ protection matching layer 24, shown in Figure 24 (b), acoustic matching layer 25 is set.In the present embodiment, acoustic matching layer 25 is formed by desiccant gel.
In the present embodiment, at first, after the acoustic matching layer 25 that forms thickness shown in Figure 24 (b), shown in Figure 24 (c) with acoustic matching layer 25 attenuates.At this moment, set the thickness L3 of protection matching layer 24 and the thickness L1 of acoustic matching layer, (=L3-L1) equals a hyperacoustic wavelength in the air to make distance L shown in Figure 20 2.Particularly, be 500kHz because frequency of ultrasonic is accepted in transmission, so the aerial wavelength of this ultrasound wave is 0.62mm.On the other hand, because the thickness L3 of protection matching layer 24 is 1.0mm, so the thickness L1 of acoustic matching layer 25 is 0.32mm (=1.0mm-0.62mm).And, suitably have function in order to make acoustic matching layer 25 as acoustic matching layer, preferably this thickness L1 (=0.32mm) be 1/4 of the ultrasound wave wavelength of propagating acoustic matching layer 25.Therefore, indispensability has the material behavior that makes 0.32mm become the velocity of sound of transmission reception ultrasound wave wavelength 1/4.According to calculating, be that to form thickness be that the acoustic matching layer 25 of 0.32mm gets final product for the desiccant gel of 640m/s by the velocity of sound.
Also have, though the thickness of preferably protecting matching layer 24 is not limited to this size for 1/4 of ultrasound wave wavelength in the protection matching layer 24.Getting final product in the scope below 1/3 more than 1/8 of ultrasound wave wavelength, better in the scope below 1/4 more than 1/6 at the ultrasound wave wavelength.Having at this ultrasound wave under the situation of Wavelength distribution, preferably can be benchmark decision thickness with the peak wavelength.Have in this manual under the situation of Wavelength distribution, so-called " wavelength 1/4 " means " peak wavelength 1/4 ".
At acoustic matching layer 25 is under the situation of individual layer, the thickness of also preferred acoustic matching layer 25 be in the acoustic matching layer 25 the ultrasound wave wavelength 1/4, but be not limited to this size.Getting final product in the scope below 1/3 more than 1/8 of ultrasound wave wavelength, better in the scope below 1/4 more than 1/6 at the ultrasound wave wavelength.At acoustic matching layer is under the situation of multilayer, and preferred each formation layer all has above-mentioned thickness.Have the ultrasonic transmitter-receiver that acoustic matching layer is a sandwich construction, narrate in the back as second embodiment.
As the material of the desiccant gel that constitutes acoustic matching layer 25, can use various materials such as inorganic material, high-molecular organic material.Solid skeletal portion as inorganic material can use monox, aluminium oxide, titanium dioxide etc.And the solid skeletal portion as high-molecular organic material can use general thermoset resin, thermoplastic resin etc., for example, can use polyurethane, polyureas, phenol resin, polyacrylamide, polymethylmethacrylate etc.
In the present embodiment,, consider, adopted the desiccant gel that has as the monox of solid skeletal portion from the difficulty or ease of cost, environmental stability, manufacturing, the stable aspects such as temperature characterisitic of ultrasonic transmitter-receiver as the material of acoustic matching layer 25.
The velocity of sound of 640m/s is than higher value as the velocity of sound of desiccant gel.Therefore, in the present embodiment, formation is during as the desiccant gel layer of acoustic matching layer 25, not to adopt the method always of then carrying out drying process in gelation operation (to call " the first gelation operation " in the following text) afterwards, but adopt the method for after the first gelation operation, carrying out the second gelation operation.
Only carry out under the situation of the first gelation operation not carrying out the second gelation operation, be difficult to obtain expressing the desiccant gel of the high velocity of sound, also have, because the density of desiccant gel increases pro rata with the velocity of sound substantially, so " the high velocity of sound " also means " high density ".If with the velocity of sound that improves gel is purpose, increase the concentration of gel raw material in the gel material liquid, gelation reaction can not carry out equably, forms the moistening gel with velocity of sound stochastic distribution.Also can have at random Density Distribution by the desiccant gel that will this moistening gel drying obtains.Therefore, when the concentration of gel raw material increased in the gel material liquid, the homogenising of the velocity of sound is difficulty very.
In the present embodiment, for fear of the uneven homogenize of gel, the velocity of sound with the desiccant gel that forms in the first gelation operation is adjusted in below about 200m/s, by the second gelation operation density is further risen, and the velocity of sound equably rises.In the second gelation operation, carry out resulting moistening gel in the first gelation operation is immersed in dip treating in the gel material liquid (the second gel material liquid) again.And, in the second gelation operation, will adjust lowlyer as the concentration of the ammonia of catalyzer in the second gel material liquid.Therefore, gelation can not take place in the outside of resulting moistening gel in the first gelation operation.But, the inside of resulting moistening gel in the first gelation operation, the adhesion that has the second gel material liquid in the first gelation operation in the formed skeleton is grown up.Therefore, even do not take place under the condition of gelation at gel material liquid self, this reaction is also carried out.Like this, the variation of the velocity of sound of gel, density all is possible.
Particularly, by implementing operation shown below, form acoustic matching layer 25 by desiccant gel.
The preparation of 1: the first gelation gel of operation material liquid
With tetraethoxysilane/ethanol/water/hydrogen chloride in molar ratio 1:2:1:0.00078 mix, placed in 65 ℃ the calibration cell 3 hours, carry out the water decomposition that adds of tetraethoxysilane.And then, add mixed water/NH in the ratio (for the mol ratio of tetraethoxysilane) of 2.5/0.0057 3, prepare the gel material liquid.
2: the first gelation operations of operation
The gel material liquid (the first gelation material liquid) of above-mentioned modulation is splashed into by in piezoelectrics 22 and the protection matching layer 24 formed spaces.At this moment, the thin slice of special teflon system is arranged, form the frame that the gel material liquid is overflowed at the periphery twisting cohesion of outermost protection matching layer 24.
The sample level in 50 ℃ calibration cell that has splashed into the gel material liquid was kept about one day.Like this, supply to piezoelectrics 22 and the gel material liquid gelation of protecting in the matching layer 24 formed spaces, form moistening gel.
3: the second gelation operations (adjustment of the velocity of sound, density) of operation
Intactly carry out under the situation of drying process for resulting acoustic matching layer in the first gelation operation, density is about 2.0 * 10 2Kg/m 3, the velocity of sound is 200m/s.In the present embodiment, be that purpose is carried out the second gelation operation with the further raising velocity of sound, density.
At first, to in the first gelation operation, clean by resulting moistening gel with ethanol, prepare the second gelation material liquid,, used tetraethoxysilane/ethanol/0.1 regulation ammoniacal liquor 60:35:5 raw materials mixed liquid by volume as the second gelation material liquid.
To be immersed in the second gelation material liquid in the closed container by resulting piezoelectrics 22/ complex that moistening gel/protection matching layer 24 is constituted in the first gelation operation, in 70 ℃ calibration cell, place about 48 hours.Make in the resulting gel skeleton growth of the first gelation operation by this second gelation operation, improve density, the velocity of sound.
Operation 4: hydrophobization operation
Though the hydrophobization operation is not to be necessary, because moisture absorption can cause the deterioration of performance, so preferred practice.The hydrophobization operation is after the second gelation operation, with ethanol in the moistening gel after the second residual gelation material liquid replaces, cleans, in the hydrophobization liquid that obtains in that dimethyldimethoxysil,ne/ethanol/10% ammoniacal liquor is mixed by weight 45:45:10, flooded about one day at 40 ℃, carry out the hydrophobization operation.
Operation 5: drying process
For from obtaining desiccant gel, carry out drying process by the resultant moistening gel of above operation.In the present embodiment, as drying means, used supercritical drying.As mentioned above, desiccant gel is the porous body of very little nano-scale, by the thickness of skeleton part, the intensity of combination, the size of hole, when making the solvent seasoning from moistening gel to desiccant gel, exists to cause the situation of destruction by the tension force on solvent surface.
Therefore, it is useful utilizing the inoperative supercritical drying of surface tension.Particularly, replace above-mentioned hydrophobization liquid with ethanol after, will be by the complex of the resulting piezoelectrics 22/ moistening gel/acoustic matching layer 25 of the above operation pressure vessel of packing into, replace ethanol in the moistening gel by liquid carbon dioxide.
And then, by with liquid carbon dioxide with being pumped into container, make the pressure in the container rise to 10MPa., be warmed up to 50 ℃, make to be in supercriticality in the container thereafter.Then under the state of 50 ℃ of maintenances, slowly relief pressure is to finish drying.
Operation 6: thickness is adjusted operation
It is the acoustic matching layer 25 of 0.32mm that the desiccant gel layer grinding on lathe that forms like this formed thickness.
The density of the desiccant gel of the formation acoustic matching layer 25 that obtains like this is about 0.6 * 10 3Kg/m 3, the velocity of sound is 640m/s.And, though also being become the desiccant gel of acoustic matching layer 25, the part of protection matching layer 24 soaks into, do not influence the velocity of sound of protection matching layer 24.
Before forming the operation of acoustic matching layer by desiccant gel, preferably can handle the surface of electrode 23b, make between electrode 23b and the acoustic matching layer 25 to have good fluid-tight engagement.Fluid-tight engagement by between surface treatment increase electrode 23b and the acoustic matching layer 25 can further improve reliability.As such surface treatment, can adopt and the easy chemically combined electrode Cement Composite Treated by Plasma etc. of giving hydroxyl of desiccant gel on the piezoelectrics surface.Or forming concavo-convex by the surface at electrode 23b also is effective to give fixed effect.Particularly, can adopt suitable chemistry and/or physics corrosion treatment.
In the present embodiment, become the gel of acoustic matching layer 25 in formation after, carry out grinding by lathe, adjust the thickness of desiccant gel.The adjusting of thickness also can be undertaken by the amount (highly) that is adjusted at the first gelation material liquid that drips in the first gelation operation.In this case, in order to form finally the have an appointment thickness of 0.32mm of acoustic matching layer, correctly measure the gel material liquid of 33.9 μ L, drip on the piezoelectrics 22 by micro-pipette.Because protection matching layer 24 is the porous plastids with 80% hole, so the amount that the volume calculation that is necessary to absorb according to porous plastid is dripped.
The transmission of the ultrasonic transmitter-receiver of Zhi Zaoing receives waveform and is shown in Figure 25 like this.In Figure 25, solid line represents that the ultrasound wave of present embodiment send to receive waveform, and the protection portion with same thickness sends the reception waveform by shown in the dotted line with the ultrasound wave of the ultrasonic transmitter-receiver (comparative example) of acoustic matching layer 25.As shown in Figure 25, the signal amplitude of present embodiment increases.Use structure of the present invention can reach high sensitivityization.
In the present embodiment; for with the position of same level above the protection matching layer 24 on hyperacoustic phase place of aliging; the ultrasound wave of propagating acoustic matching layer 25 and propagation medium 26 and coming; the ultrasound wave that comes with propagating overprotection matching layer 24 is compared, and the phase delay of a wavelength part takes place just.In the situation that is forming protection matching layer 24 by material and will protect the thickness L3 of matching layer 24 to set to such an extent that wait greatly under the situation, also can phase delay be set at hyperacoustic two more than the wavelength by propagation medium 26 with bigger velocity of sound.
(the 11 embodiment)
Then, with reference to Figure 26 the 11 embodiment of ultrasound wave transceiver of the present invention is illustrated.The principal feature of present embodiment is, have acoustic matching layer comprise lower floor the first acoustic matching layer 25a, with the rhythmo structure of the second sound matching layer 25b on upper strata.
Have at acoustic matching layer 25 under the situation of double-layer structure, the thickness of also preferred each acoustic matching layer 25a, 25b is set at about 1/4 of ultrasound wave wavelength in the acoustic matching layer separately respectively.
In the present embodiment; same with the tenth embodiment; for with the position of same level above the protection matching layer 24 on hyperacoustic phase place of aliging; the ultrasound wave of propagating acoustic matching layer 25 and propagation medium 26 and coming; the ultrasound wave that comes with propagating overprotection matching layer 24 is compared, and the phase delay that ultrasound waves is about integral multiple takes place.
In structure shown in Figure 25, ultrasonic propagation overprotection matching layer 24 and when arriving protection matching layer 24 top arrives the boundary face of first acoustic matching layer and second sound matching layer 25b with the synchronous ultrasound wave of this ultrasound wave.This is because the little cause of the velocity of sound of the velocity of sound ratio protection matching layer 24 of the first acoustic matching layer 25a.Ultrasound wave above the first acoustic matching layer 25a arrival second sound matching layer 25b below, and then need the 1/4f time of (second).Therefore, the time set that arrives if will propagate sonic propagation medium 26 above second sound matching layer 25b with same level above the protection matching layer 24 will be 3/4f (second), just can be with the last area levelling of protecting matching layer 24 with phase alignment.Adopt such structure, transmitted sound matching layer 25a and 25b and the ultrasound wave that radiates, and see through protection matching layer 24 and between the ultrasound wave of radiation, the delay of a wavelength part takes place are interfered mutually and are strengthened owing to two ultrasound waves, make hyperacoustic amplitude increase.
Manufacture method to acoustic matching layer 25a and 25b in the present embodiment is illustrated below.
At first, same with the manufacture method of acoustic matching layer 25 in the tenth embodiment, make protection matching layer 24.Material as protection matching layer 24 uses porous ceramic, and its thickness (L7) is set at 1.0mm.
In the present embodiment, will the distance (L6) to the last area levelling of protecting matching layer 24 be set at 0.51mm above second sound matching layer 25b, making the travel-time in propagation mediums such as air 26 is 3/4f (second).Consequently the aggregate thickness (L4+L5) of the first acoustic matching layer 25a and second sound matching layer 25b equals 0.49mm.
In the present embodiment, when the velocity of sound of setting second sound matching layer 25b is 200m/s, preferably the thickness (L5) of second sound matching layer 25b can be set at 0.10mm.During L5=0.10mm, the thickness of the first acoustic matching layer 25a (L4) is 0.39mm (0.49mm-0.10mm).For the thickness that makes the first acoustic matching layer 25a is equivalent to 1/4 of ultrasound wave wavelength among the first acoustic matching layer 25a, must make the velocity of sound among the first acoustic matching layer 25a is 780m/s.
Then, above-mentioned two-layer acoustic matching layer 25a, the method for making of 25b are illustrated.The unique point of this method is, carries out the second gelation operation that is realized in two order, ten embodiments.That is to say, in the present embodiment, the second gelation operation (2-1 gelation operation) that gelation is not carried out in the outside of carrying out the moistening gel that forms in by the first gelation operation is also carried out the second gelation operation (2-2 gelation operation) that gelation produces afterwards in the outside of moistening gel.
In the present embodiment, at first, by implement with the tenth embodiment in the same operation of practiced operation 1～operation 6, form the first acoustic matching layer 25a.But the second gelation operation of this moment is a 2-1 gelation operation.
The increase of prediction acoustic impedance in the 2-2 gelation operation of carrying out subsequently in 2-1 gelation operation, can be saved and makes the density of the first acoustic matching layer 25a be about 0.5 * 10 3Kg/m 3, the velocity of sound is the processing time about 500m/s.In the present embodiment, the processing time is shorter than the processing time of second gelation in the tenth embodiment, is set at about 36 hours.
Then, by carrying out 2-2 gelation operation, in the acoustic impedance that increases by the first acoustic matching layer 25a, form second sound matching layer 25b on the top of the first acoustic matching layer 25a.This 2-2 gelation operation, following particularly carrying out.
2-2 gelation operation
At first, as 2-2 gelation material liquid, prepare liquid with tetraethoxysilane/ethanol/0.05 regulation ammoniacal liquor 1:4:3 mixing in molar ratio.With this 2-2 gelation material liquid, be filled in by in the first acoustic matching layer 25a and the protection matching layer 24 formed spaces.Then, by intactly placing 24 hours, finish gelation in room temperature.Like this, in the acoustic impedance of adjusting the first acoustic matching layer 25a, form moistening gel as second sound matching layer 25b.
Subsequently, same with the tenth embodiment, adjust operation by carrying out hydrophobization operation, drying process and thickness, finish acoustic matching layer 25a, 25b. Acoustic matching layer 25a, 25b in the present embodiment have following feature.
The first acoustic matching layer 25a
Density: 0.7 * 10 3Kg/m 3, the velocity of sound: 780m/s
Acoustic impedance: 5.46 * 10 5Kg/m 2/ s
Thickness: 0.39mm
Second sound matching layer 25b
Density: 0.2 * 10 3Kg/m 3, the velocity of sound: 200m/s
Acoustic impedance: 4.0 * 10 4Kg/m 2/ s
Thickness: 0.10mm
The transmission of the ultrasonic transmitter-receiver of present embodiment receives waveform and is shown in Figure 27.In Figure 27, the ultrasound wave of the ultrasonic transmitter-receiver of present embodiment send to receive waveform to be represented by solid line, and the sound protective seam with same thickness sends the reception waveform by shown in the dotted line with the ultrasound wave of the ultrasonic transmitter-receiver (comparative example) of acoustic matching layer.As shown in Figure 27, can realize high sensitivityization according to the ultrasonic transmitter-receiver of present embodiment.
In the present embodiment, acoustic matching layer 25 is to be made of two-layer institute but also can be more than three layers, by design, makes phase place consistent on protection matching layer 24, can obtain same effect.
(the 12 embodiment)
With reference to Figure 28 the 12 embodiment of the present invention is illustrated.The unique point of present embodiment is that the first acoustic matching layer 25a is integrally formed by identical materials with protection matching layer 24.Top at the first acoustic matching layer 25a forms by the formed second sound matching layer of desiccant gel 25b.
In the present embodiment, the first acoustic matching layer 25a equates with wavelength with the ultrasonic velocity of protection in the matching layer 24, and, protect the thickness L11 of matching layer 24 to be set at 1/4 of ultrasound wave wavelength.Therefore, the thickness L8 of the first acoustic matching layer 25a is littler than hyperacoustic 1/4 wavelength.The thickness L8 of the first acoustic matching layer 25a is by the thickness L9 of second sound matching layer 25b, determined with the distance L 10 to the last area levelling of protection matching layer 24 above second sound matching layer 25b.
In the present embodiment, also adopt transmitted sound matching layer 25a and 25b and the ultrasound wave that radiates, and see through protection matching layer 24 and between the ultrasound wave of radiation, produce the structure of ultrasound waves lint-long integer phase delay doubly.Therefore, area levelling on protection matching layer 24 was propagated acoustic matching layer 25a, 25b and sonic propagation medium 26 and the ultrasound wave of arrival, and its phase place is consistent.
The hyperacoustic sensitivity that comes in order to improve transmitted sound matching layer 25a and 25b is compared with the thickness of the first acoustic matching layer 25a, and the thickness of second sound matching layer 25b is even more important.In the present embodiment, the thickness setting with second sound matching layer 25b receives about 1/4 of ultrasound wave wavelength for sending.Though the thickness of the first acoustic matching layer 25a is also influential to sensitivity, its influence more is the ratio frequency band to frequency.
Therefore, in the present embodiment, at first from the viewpoints such as physical strength of material, decision can constitute the characteristic of the desiccant gel layer of second sound matching layer 25b.Then, decision by with the thickness L8 of the protection matching layer 24 same materials formed first acoustic matching layer 25a and the thickness L10 of sonic propagation medium.
In the present embodiment, the material as protection matching layer 24 similarly uses porous ceramic with above-mentioned embodiment, and (L11) is set at 1/4 of ultrasound wave wavelength with its thickness.Exactly L11 is set at 1.0mm.In this case, be 200m/s by the velocity of sound of the formed first acoustic matching layer 25b of above-mentioned porous ceramic, density 0.2 * 10 3Kg/m 3For the thickness setting of the second sound matching layer 25b that will be formed by desiccant gel is 1/4 of a ultrasound wave wavelength, setting L9 is 0.10mm.
At this moment, there is following formula (6) to set up.
L8+L10＝0.9(mm) (6)
Formula (6) is to be set at 1.0mm by L11, and L9 is set at that 0.1mm derives.
In order to bring into play excellent characteristic, preferably have following formula (7) and set up.
L8/1+L10/ (17/25)=1 (wavelength) (7)
In the present embodiment, owing to be that the transmission receive frequency is the ultrasound wave of 500kHz, so a hyperacoustic wavelength is 1.0mm among the acoustic matching layer 25a, a hyperacoustic wavelength is 17/25mm in the sonic propagation medium 26.Formula (7) is the thickness L8 of the first acoustic matching layer 25a and the ratio of 1 wavelength of ultrasound wave, and the thickness L10 of propagation medium 26 and the ratio sum of 1 wavelength of ultrasound wave.Satisfy formula (8), mean the ultrasound wave wavelength that only advanced when seeing through the first acoustic matching layer 25a and sonic propagation medium 26.In other words, the actual effect thickness of experiencing hyperacoustic first acoustic matching layer 25a and sonic propagation medium 26 is a wavelength.
Calculate and satisfy formula (6) and formula (7) L8 and L10, draw the about 0.69mm of L8=, L10=0.21mm.
Then, with reference to Figure 29 (a)～(d), the manufacture method of the ultrasonic transmitter-receiver of present embodiment is illustrated.
At first, shown in Figure 29 (a), prepare by porous ceramic constitute, thickness is the disk of 1.0mm, this disk is processed shown in Figure 29 (b).In the present embodiment, formation groove on disk is 0.69mm with the thickness adjusted of channel bottom.This channel bottom is the part as the function of the first acoustic matching layer 25a.Groove forms ring-type as shown in figure 21.
Then, shown in Figure 29 (c), at the inner second sound matching layer 25b that forms of groove.The thickness of second sound matching layer 25b is 0.1mm.Shown in Figure 29 (d),, form ultrasonic transmitter-receiver 21 with protecting the complex of matching layer 24/ acoustic matching layer 25a, 25b to be engaged in piezoelectrics 22.
The first acoustic matching layer 25b is to use tetramethoxy-silicane/ethanol/0.05 regulation ammoniacal liquor liquid of mixing of the ratio of 1:7:4 in molar ratio, and is same with first embodiment, forms by carrying out the first gelation operation.
The complex that is made of protection matching layer 24/ acoustic matching layer 25a, 25b engages with piezoelectrics, and is same with first embodiment, is that cementing agent carries out by epoxy.
According to present embodiment,,, reduce manufacturing cost so can simplify manufacturing process because protection matching layer 24 can form with acoustic matching layer 25a.
(the 13 embodiment)
With reference to Figure 30 the 13 embodiment of the present invention is illustrated.The unique point of present embodiment is to have structural support.
The ultrasonic transmitter-receiver of present embodiment except having the structural support 7 between piezoelectrics 22 and first acoustic matching layer 25 and protection matching layer 24, sends the receiving record carrier with the ultrasound wave of first embodiment and has identical structure.
Structural support 7 is provided with the discoid support portion of fixed sound matching layer 25 grades, with the cylindrical portion of axially extending continuously from this discoid support portion.The end face of cylindrical portion, its cross section bend to " L " type, form the shape be fixed on easily on the plate (not shown) that is used to cover piezoelectrics 22 and other the device etc.
Surface configuration in structural support 7 has acoustic matching layer 25 and protection matching layer 24, disposes piezoelectrics 22 at the back side, support portion.By using such structural support 13, make the operation of ultrasonic transmitter-receiver very easy.
Structural support can be made of sealable container (Sensor box).In this case, if the open end of the cylindrical portion of structural support 27 is stopped up by covering with plate, and structural support 27 inside are full of inert gas, then the fluid of piezoelectrics 22 from the measurement of rate of flow object can be cut off.
In order to apply voltage, if piezoelectrics contact inflammable gas, the danger that then has inflammable gas to ignite to piezoelectrics 22.But because structural support 27 is made of the leakproofness container, even some partitions inner and external fluid by with piezoelectrics 22 can prevent such igniting, so for inflammable gas, also can send the reception ultrasound wave safely.
And, even outside gas is not inflammable gas, with piezoelectrics 22 reactions, may make to send in the gas of characteristic degradation of piezoelectrics 22 and receive under hyperacoustic situation, preferably piezoelectrics 22 and extraneous gas are cut off.Thus, prevent the deterioration of piezoelectrics 22, can in long-time, realize the high work of reliability.
In the structural support 27, the part between piezoelectrics 22 and acoustic matching layer 25, protection matching layer 24 does not have the function as acoustic matching layer.Therefore, sound is not constituted obstacle in order to make structural support 27, in the preferred structure supporter 27, the thickness of the part between piezoelectrics 22 and acoustic matching layer 25, protection matching layer 24 can send the about below 1/8 of reception ultrasound wave wavelength.
In the present embodiment, structural support 27 is formed by stainless steel, and the thickness setting of above-mentioned part is 0.2mm.
The velocity of sound in the stainless steel is about 5500m/s, and hyperacoustic wavelength of 500kHz is about 11mm.Because the thickness of 0.2mm is equivalent to the about 1/55 of wavelength, so the existence of structural support 27 can become the essential factor that acoustic resistance hinders hardly.
The material of structural support 27 is not limited to stainless steel and other metal materials, can select pottery, glass, resin etc. according to purpose.In the present embodiment, in order reliably the fluid of outside being separated with piezoelectrics, also can to prevent the intensity that piezoelectrics contact with external fluid, to have made structural support 27 by metal material even make when structural support applied some physical shock.Thus, even be that object carries out hyperacoustic transmission reception for example, also can guarantee high security to have combustibility and volatile gas.
Also having, under the situation of carrying out hyperacoustic transmission reception for security gas, is purpose to reduce the cost, and also can form structural support by materials such as resins.
(the 14 embodiment)
With reference to Figure 31 (a) and (b), the 14 embodiment of ultrasonic transmitter-receiver among the present invention is illustrated.It is the vertical view of present embodiment that Figure 31 (a) reaches (b).
In example shown in Figure 21; use ring (three endless members of same widths different-diameter) as the porous ceramics system of protection matching layer 24 functions; its center as one man is configured on the interarea of piezoelectrics; but also can shown in Figure 31 (a), use the different ring of width to form protection matching layer 24.And, can also be shown in Figure 31 (b), with protection matching layer 24 random arrangement of island.
At protection matching layer 24 and acoustic matching layer 25 regularly under the situation on the interarea of alignment arrangements at ultrasonic transmitter-receiver, hyperacoustic phase place unanimity on the direction that is angle for its interarea, amplitude is strengthened.This is called as " secondary lobe ", becomes the obstruction essential factor in the ultrasonic measurement.But, as shown in figure 31, do not have periodic structure by the arrangement of adopting protection matching layer 24, can suppressed sidelobes, can carry out the ultrasonic measurement of high precision and high reliability.
(the 15 embodiment)
With reference to Figure 32 the 15 embodiment of ultrasonic transmitter-receiver among the present invention is illustrated.
First of the ultrasonic transmitter-receiver of present embodiment is characterised in that the thickness of protection matching layer 24 has distribution in face.In the respective embodiments described above, the thickness of protection matching layer 24 all is set at the same in face, but in the present embodiment, distributes consciously in face.And second of present embodiment is characterised in that the protection matching layer 24 that is provided with is made of two kinds of different materials on piezoelectrics 22.
According to the structure of present embodiment, distribute in the face of different-thickness by adopting different materials and/or giving, can suppressed sidelobes, change to send receiving frequency of ultrasonic, realize broad in band.
Also have, preferably respectively protect the thickness of matching layer 24 to be included in the scope more than 1/8, below 1/3 of ultrasound wave wavelength, preferred being included in the long scope more than 1/6, below 1/4 of ultrasound waves.But the thickness of a part with protection matching layer 24 of different-thickness also can be outside above-mentioned scope.Do not have the function of acoustic matching layer owing to have the protection matching layer 24 of thickness outside the above-mentioned scope, so be that ultrasound wave sends the sensitivity decline that receives.But, be positioned over the appropriate location on the piezoelectrics by the protective seam (not being called " protection matching layer ") that will not have the function of acoustic matching layer, can prevent the disorder of ultrasonic proximity field, realize good ultrasonic measurement.
(the 16 embodiment)
With reference to Figure 33 the embodiment of ultrasonic flow meter among the present invention is illustrated.
The ultrasonic flow meter of present embodiment is provided with determined fluid and flows through in the pipe that has as the function of flow measurement portion 51 with speed V.On the tube wall 52 of flow measurement portion 51, opposite face disposes ultrasonic transmitter-receiver 1a and the 1b that is made of ultrasonic transmitter-receiver of the present invention.
At a time, ultrasonic transmitter-receiver 1a has the function as ultrasound transmitter device, ultrasonic transmitter-receiver 1b has the function as ultrasonic receiver, but constantly at another, ultrasonic transmitter-receiver 1a has the function as ultrasonic receiver, and ultrasonic transmitter-receiver 1b has the function as ultrasound transmitter device.Such switching is to be undertaken by circuit switched 53.
Ultrasonic transmitter- receiver 1a, 1b are connected by the reception detection line 55 of circuit switched 53 with the driver circuit 54 that drives ultrasonic transmitter- receiver 1a, 1b, detection ultrasonic pulse.Receive the output of detection line 55, deliver to the timer 56 that detects the ultrasonic pulse travel-time.The calculation portion 57 of calculated flow rate is delivered in the output of timer 56.In calculation portion 57, based on the travel-time of the ultrasonic pulse of measuring, calculate the flow velocity V that flows through flow measurement portion 51 inner fluids, obtain flow.Driver circuit 54 and timer 56 are connected with control part 58, are controlled by the control signal of control part 58 outputs.
Below, the work of this ultrasonic flow meter is described in detail.
As determined fluid, consider the situation of LP gas stream inflow-rate of water turbine determination part 51.If the driving frequency of ultrasonic transmitter- receiver 1a and 1b is about 500kHz.Control part 58 begins clocking of timer 56 in the time of driver circuit 54 output proceed-to-send signals.When driver circuit 54 receives proceed-to-send signal, drive ultrasonic transmitter-receiver 1a, send ultrasonic pulse.The ultrasonic pulse that sends is in flow measurement portion 51 and propagate, and 1b receives by ultrasonic transmitter-receiver.The ultrasonic pulse of accepting is transformed to electric signal at ultrasonic transmitter-receiver 1b, outputs to receive detection line 55.
Receive the time of reception of detection line 55 decision received signals, stop timer 56.Travel-time t1 calculates in calculation portion 57.
Then, the ultrasonic transmitter-receiver 1a and the 1b that will be connected in driver circuit 54 by circuit switched 53 and receive detection line 55 switches.And again, control part 59 begins clocking of timer 56 in the time of driver circuit 54 output proceed-to-send signals.Opposite with the mensuration of travel-time t1, send ultrasonic pulse by ultrasonic transmitter-receiver 1b, ultrasonic transmitter-receiver 1a receives, and travel-time t2 calculates in calculation portion 57.
Here, if connecting the distance at the center of ultrasonic transmitter-receiver 1a and ultrasonic transmitter-receiver 1b is L, the velocity of sound of the windless condition of LP gas is C, flow velocitys in the flow measurement portion 51 are V, the flow direction of determined fluid, with the line angulation at the center of ultrasonic transmitter-receiver 1a and ultrasonic transmitter-receiver 1b be θ.
Travel-time t1, t2 are obtained by mensuration respectively.Because distance L is known, so minute t1 and t2 can obtain flow velocity V, V can determine flow by this flow velocity.
In such ultrasonic flow meter, travel-time t1, t2 are measured by the method that is called as zero crossing.In the method,, set suitable valve level, measure to surpass the next amplitude of this valve level and be the time of zero point for the reception waveform shown in Figure 21 (a).Under the bad situation of the S/N of received signal, because amplitude is some change in time by noise level of zero, can not correctly measure t1, t2 so have, be difficult to correctly measure the situation of flow.
As the ultrasonic transmitter-receiver of such ultrasonic flow meter, if use ultrasonic transmitter-receiver of the present invention, the S/N of received signal is improved, measure t1, t2 accurately.
Shown in Figure 21 b, compare with the situation of Figure 21 (a), if the startup of received signal slow (narrow-band), the position at peak of then measuring the received signal of t1, t2 can change for valve level setting value, may produce error at measurment, still, because ultrasonic transmitter-receiver of the present invention can suitably be worked in broadband, so the startup of received signal is good, can stably carry out correct flow measurement.Also have,, preferably use by the mean value of repeatedly measuring resulting value as the value of t1, t2.
What is called can send and receive the broadband ultrasound wave, means that the end of signal is also fast.Therefore, even carrying out fast under the situation of replication, also can not be subjected to the influence of former transmission received signal.Consequently, even improve the frequency of replication, also can carry out instantaneous mensuration, so can be used for the instantaneous detections such as leakage of gas.
In each above embodiment, be to expose above the acoustic matching layer of the superiors (first acoustic matching layer), but also in the above cladding thickness be the following diaphragms of 10 μ m.Such diaphragm can avoid atmosphere to contact with the direct of acoustic matching layer, is useful for the characteristic of long-term maintenance acoustic matching layer.Diaphragm for example can be made of the formed film of materials such as aluminium, monox, low-melting glass, macromolecule (being not limited to individual layer).Diaphragm can be formed by sputtering method, CVD method.
According to the present invention, used the high performance ultrasonic transmitter-receiver of the formed thin layer acoustic matching layer of the material extremely low by acoustic impedance, that physical strength is little, can practicability.Can also improve the reliability when using.In first form of the present invention, owing to be provided with protection acoustic matching layer the time, can also be used for the protection portion of the thickness of regulation acoustic matching layer, so can high precision, repeatability forms low, the thin acoustic matching layer of physical strength well.Consequently can provide can be with the high wide band ultrasound wave of sensitivity transmission reception, the ultrasonic transmitter-receiver that reliability is high.And, in second form of the present invention, have the protection portion (protection portion hold concurrently acoustic matching layer=protection matching layer) of acoustic matching layer function can be in the interarea of piezoelectrics arbitrarily the position be provided with.By the velocity of sound and the thickness of regulating two kinds of acoustic matching layers, can make from two kinds of different hyperacoustic phase place unanimities that acoustic matching layer radiated of thickness, can improve hyperacoustic transmission receiving sensitivity.

Claims (17)

1. ultrasonic transmitter-receiver; it is characterized in that: have piezoelectrics; the lower floor's acoustic matching layer that on described piezoelectrics, is provided with; the upper strata acoustic matching layer that on described lower floor acoustic matching layer, is provided with; and contact, be arranged at protection portion for described piezoelectrics fixed position with at least a portion of the side of described upper strata acoustic matching layer
Described upper strata acoustic matching layer is 50kg/cm by density 3Above 1000kg/cm 3Following material forms,
Described protection portion is made of the part institute of described lower floor acoustic matching layer, and integrated with described lower floor acoustic matching layer.
2. ultrasonic transmitter-receiver according to claim 1; it is characterized in that: described protection portion is from outstanding to the ultrasonic wave radiation direction on the plane of same level with the interarea of described lower floor acoustic matching layer, is the thickness that the height of the described protection portion of benchmark is stipulated described upper strata acoustic matching layer with the interarea of described lower floor acoustic matching layer.
3. ultrasonic transmitter-receiver according to claim 1 and 2 is characterized in that: the described height of described protection portion is below the above 2500 μ m of 5 μ m.
4. ultrasonic transmitter-receiver according to claim 3 is characterized in that: the thickness of described upper strata acoustic matching layer equates with the described height of described protection portion.
5. ultrasonic transmitter-receiver according to claim 1 is characterized in that: the thickness of described upper strata acoustic matching layer is 1/4 of the ultrasound wave wavelength that sent and/or received by described piezoelectrics.
6. ultrasonic transmitter-receiver according to claim 1 is characterized in that: described upper strata acoustic matching layer is to be 2.5 * 10 by acoustic impedance 3Kg/m 2/ s above 1.0 * 10 6Kg/m 2The following material of/s forms.
7. ultrasonic transmitter-receiver according to claim 6 is characterized in that: described upper strata acoustic matching layer is formed by inorganic based material.
8. ultrasonic transmitter-receiver according to claim 7 is characterized in that: described inorganic based material is the desiccant gel of inorganic oxide.
9. ultrasonic transmitter-receiver according to claim 8 is characterized in that: described inorganic oxide has hydrophobization solid skeletal portion.
10. ultrasonic transmitter-receiver according to claim 1 is characterized in that: described upper strata acoustic matching layer be on the described lower floor acoustic matching layer that is provided with described protection portion by mobile state solidified material.
11. ultrasonic transmitter-receiver according to claim 1 is characterized in that: and then be provided with the structural support that supports described piezoelectrics.
12. ultrasonic transmitter-receiver according to claim 1 is characterized in that: the surface treatment that hydroxyl is given at least a portion acceptance of the surface of contact of described upper strata acoustic matching layer and described protective seam.
13. ultrasonic transmitter-receiver according to claim 1 is characterized in that: at least a portion of the surface of contact of described upper strata acoustic matching layer and described protective seam is accepted the asperities processing.
14. ultrasonic transmitter-receiver according to claim 1 is characterized in that: at least a portion of the surface of contact of described upper strata acoustic matching layer and described protective seam is a porous matter.
15. ultrasonic transmitter-receiver according to claim 1 is characterized in that: the elastic modulus of described protection portion equates with the elastic modulus of described acoustic matching layer.
16. a ultrasonic flow meter is characterized in that being provided with:
The flow measurement portion that determined fluid flows through;
Be arranged at a pair of ultrasonic transmitter-receiver of described flow measurement portion, transmission and received ultrasonic signal;
The measurement mechanism in travel-time of measuring ultrasound wave between described a pair of ultrasonic transmitter-receiver; And
Based on the calculation apparatus of the calculated signals outflow of described measurement mechanism,
Wherein said a pair of ultrasonic transmitter-receiver is respectively the described ultrasonic transmitter-receiver of claim 1.
17. ultrasonic flow meter according to claim 16 is characterized in that: the piezoelectrics of described ultrasonic transmitter-receiver and described determined fluid separate.
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