CN1039867C

CN1039867C - Ultrasonic transducer

Info

Publication number: CN1039867C
Application number: CN91102579.0A
Authority: CN
Inventors: 巴里·约翰·马丁
Original assignee: Alg Consulting Co Ltd; Commonwealth Scientific and Industrial Research Organization CSIRO
Current assignee: Alg Consulting Co Ltd; Commonwealth Scientific and Industrial Research Organization CSIRO
Priority date: 1990-04-27
Filing date: 1991-04-27
Publication date: 1998-09-16
Anticipated expiration: 2006-04-27
Also published as: DK0598715T3; FI924849A; SG46263A1; AU7741391A; NO924136D0; JPH05507183A; WO1991017637A1; ES2109267T3; GR3025648T3; EP0598715B1; DE69128155T2; NO924136L; CA2081472A1; ATE160069T1; NO306530B1; NZ237971A; EP0598715A4; HU9203367D0; FI924849A0; HUT64672A

Abstract

Ultrasonic piezoelectric transducer comprising a piezoelectric material (10) having a profile whereby the transducer transmits and/or receives ultrasonic vibrations in a dilational (quasilongitudinal) mode. The profile is curved and includes a point of inflection. Possesses a vibrational peak in the frequency range 10 KHz - 200 KHz. Construction is performed via profiling and tensioning the piezoelectric material.

Description

Ultrasonic transducer

The present invention relates to the ultrasound piezoelectric transducer, promptly, a kind of method that constitutes a kind of ultrasound piezoelectric transducer, a kind of system that launches ultrasonic vibration, a kind of system that detects ultrasonic vibration, the system of a kind of emission and detection ultrasonic vibration, a kind of method of launching ultrasonic vibration, a kind of method that detects ultrasonic vibration, and the method for a kind of emission and detection ultrasonic vibration.

Some accidental occasions can produce such needs, that is, frequency of utilization in the 100-200kHz scope, power demand is minimum and be operated in ultrasonic transducer in air or other gas.The requirement of the low power demand transducer that major part is existing forecloses, and how poor its sensitivity of these transducers all needs high-power excitation power supply, and perhaps whether it needs high bias voltage they all are difficult to be operated in the small-power D.C. system.For example, the ultrasonic transducer (being usually used under water) that is operated in air or other gas typically muting sensitivity with the arrowband.These characteristics are owing to exist very big acoustic impedance mismatch (latter can produce bigger strength but less deviation is only arranged) between air or other gas and the transductive material.They are not to have only less deviation (output of low-power sound wave), can only make material at a specific frequency upper resonance exactly.For the application of echo sensing and message transmission, single-frequency is useless, but needs wide as far as possible frequency range.Worked out the electrostatic transducer of some low bias voltages (30V), but they are expensive and manufacture time-consuming.

The purpose of this invention is to provide a kind of ultrasound piezoelectric transducer with piezoelectric sheet of special shape.

Another purpose provides the method for the described PZT (piezoelectric transducer) of structure.

The present invention has disclosed the piezoelectrics material with suitable shape and can be energized under a certain pattern, and this pattern is called as expansion mode or fiducial axis to pattern in this specification and claims thereof.Transducer will be explained below in detail in the implication that expansion mode is energized.When a piezoelectric with certain curved shape is energized, when being elongated, it just expands, when being shortened, it then shrinks.And under situation about not being bent, then do not have transverse movement and produce.Therefore, if material is crooked and do not have flex point by gentle ground, and therefore no change on curvilinear path, it just makes synchronous transverse vibration on whole length.On the other hand, if curve includes flex point, then lateral displacement will produce phase change at that point.If this curve that comprises flex point also has suitable radial geometry, will effectively piezoelectric excitation be coupling in lateral displacement, take this, the transverse vibration of out of phase is interfered longways mutually and is obtained high-power output, when this situation takes place, promptly be that piezoelectric is energized under expansion mode.In this manner, can be designed to be used in wavelength be on several millimeters the ultrasonic frequency of the order of magnitude to the transducer with high efficient radiation zone.

According to the present invention, a kind of PZT (piezoelectric transducer) that can transmit and receive ultrasonic vibration is provided, it comprises the shape of a saddle piezoelectric sheet of working with the device of the support and the described thin slice that stretches with matching, wherein

Described shape of a saddle thin slice is by described device moulding and stretch, and forms three bends, and wherein, between each described bend and the adjacent bend thereof opposite sign of curvature is arranged, and be not fixed on the described device, and wherein

Described thin slice is not restrained between each described portion, and is fixed on the described device with the arbitrary limit in the both sides of described three bends;

Usually, ultrasonic vibration has the vibration peak in the 10kHz-200kHz frequency range.

This scope is typically at 12kHz-160kHz, 80kKz-120kHz, 95kHz-105kHz, 10kHz-199kHz, 15kHz-60kHz or 15kHz-30kHz.In this scope, more than one vibration peak can be arranged.

In a kind of form of the present invention, transducer can be operated under the pattern of expansion, and wherein the piezoelectric excitation in the thin slice causes that to effective coupling of lateral displacement the transverse vibration phase of out of phase interferes longways and obtain high-power output.

The device of support and stretching piezoelectric sheet can be adjusted and make this material can be stretched shaping to produce and/or to receive the supersonic frequency of the ultrasonic frequency range of various requirement.

Transducer of the present invention can comprise can be in fiducial axis emission and/or receive any piezoelectric of ultrasonic vibration under/expansion mode.Such material includes polymeric piezoelectric material, piezoelectric plastics material and piezoelectricity elastomeric material.Favourable piezoelectric comprises a kind of polyethylene polymer (poled polyvinylidene polymer) of connection, PVDF, perhaps a kind of 1, the copolymer of 1-difluoroethylene and trifluoro-ethylene (copolymer of vinylidene fluoride andtrifluoroethylene), being shaped as that it is possible is tabular, sheet, film or other suitable piezoelectricity shape.

According to shape required for the present invention, this piezoelectric sheet is as being drawn in the shape of a saddle among Fig. 9, wherein, A and C are the strong point of piezoelectric, x was B A of ordering and the material shape length between the C point, d1 is the distance between A and the C point, d3 is the distance between the shape of a saddle two summits, h1 is piezoelectric is wired to shape of a saddle summit, left-hand side from A and C point a height, hr is piezoelectric is wired to right-hand side shape of a saddle summit from A and C point a height, h21 is the saddle-shaped height in piezoelectric left-hand side, and h2r is the saddle-shaped height of piezoelectric right-hand side, wherein:

1.5×d1≤x≤2.3×d1；

0.5×d1≤hr≤0.9×d1；

0.5×d1≤h1≤0.9×d1；

0.1×d1≤h21≤0.2×d1；

0.1×d1≤h2r≤0.2×d1；

0.6×d1≤d3≤0.8d1.

In a shape that needs especially of the present invention, piezoelectric sheet is the shape of a saddle that draws as Fig. 9, wherein, d2 is one and works so that the diameter of section of the rod of its stretching with piezoelectric with matching, point A and C are the strong point of piezoelectric, x was the B A of ordering and the length of the piezoelectric shape between the C point, d1 is the distance between an A and the C, d3 is the distance between the shape of a saddle two summits, h1 is the height that link to left-hand side shape of a saddle summit of piezoelectric from an A and C, hr is the height that link to right-hand side shape of a saddle summit of piezoelectric from an A and C, h21 is the saddle-shaped height in piezoelectric left-hand side, h2r is the saddle-shaped height of piezoelectric right-hand side, wherein:

1.5 ^*d ₁≤x≤2.3 ^*d ₁；

0.5 ^*d ₁≤h _r≤0.9 ^*d ₁；

0.5 ^*d ₁≤h ₁≤0.9 ^*d ₁；

0.1 ^*d ₁≤h ₂₁≤0.2 ^*d ₁；

0.1 ^*d ₁≤h _2r≤0.2 ^*d ₁；

0.05 ^*d ₁≤d ₂≤0.2 ^*d ₁；

0.6 ^*d ₁≤d ₃≤0.8 ^*d ₁.

D more typically ₁=10mm; 15mm≤x≤23mm; 5mm≤h _r≤ 9mm; 5mm≤h ₁≤ 9mm; 1mm≤h ₂₁≤ 2mm; 1mm≤h _2r≤ 2mm; 0.5mm≤d ₂≤ 2mm; And 6mm≤d ₃≤ 8mm.

Common d ₁=10mm; X=20mm; h _r=7.5mm; h ₁=7.5mm; h ₂₁=1.5mm; h _2r=1.5mm; d ₂=1.0mm; And d ₃=6.9mm.

H typically _rApproximate (within the 0.5mm scope) or equal h ₁, and h _2rApproximate (within the 0.5mm scope) or equal h ₂₁

Piezoelectric sheet advantageously comprises a kind of polyethylene sheets, and thickness is 5 μ m to 75 μ m, and it is thick typically to be 9 μ m to 35 μ m, more typically, is that 20 μ m to 25 μ m are thick, and it is thick typically to be 25 μ m most.

In its best form, piezoelectric sheet is typically by Kynoar (" PVDF ") thin slice or is made of the copolymer thin slice that comprises PVDF.This thin slice has two electrodes fixed thereon at least, and being typically on each face of thin slice has an electrode.These electrodes can be same material or different materials, are typically same material.The example of electrode material is such as metal A u, Pd, Pt, Ti, Zn, Al, Ag, Cu, Sn, Ga, In, Ni, conducting polymer, this polymer need be filled with additive, and additive is an iodine, fluorine, alkali metal and salt thereof, metal carbonate and fontanel arsenic, this conducting polymer comprises: polyyne, polyyne copolymer, polypyrrole, polyacrylonitrile, aromatic polymer, polyaniline, polythiophene, poly-card azoles, poly-beta-diketon, poly-dipropargyl amine, poly-acenaphthene/N-vinyl heterocycle lewis acid, poly-(aromatic heterocycle 1, the inferior ethene of 2-), poly-phthalocyanine, with 1, the two polymer that replace inferior benzene chemically reactive of 9-, cluster phylloerythrin, heterocyclic ladder polymer, alternative aromatics and quinoid sequence, polyisothianaphthene and poly-(right-phenylene) thioether; Do not need the polymer that mixes, for example: poly-(the two neighbour-nitriles of two ehter bonds), the poly-diine of polyacetylene and band structure cell, poly-(peri-position naphthalene), poly-(carbon diselenide), poly-(the benzo two thiol alkene) of transition metal, poly-(thiophene-sulfonic acid ester) and terminal acetylene schiff bases.

The width of general piezoelectric is 1mm-3500mm, and that favourable is 1mm-500mm, is typically 3mm-100mm, is typically 4mm-40mm, and that preferable is 5mm-20mm, and better be 10mm.

Also also having down, routine embodiment comprises within the scope of the present invention:

1. ultrasound piezoelectric transducer, it comprises having piezoelectric definite shape and that be stretched, takes this, ultrasonic vibration can be launched and/or receive to this transducer under expansion mode;

2. ultrasound piezoelectric transducer, it comprises the piezoelectric that is formed and is stretched, and takes this, ultrasonic vibration can be launched and/or receive to this transducer under expansion mode;

3. ultrasound piezoelectric transducer, it comprises having definite shape and piezoelectric that be stretched, takes this, this transducer can launch/or be received in the ultrasonic vibration at 10kHz-200kHz frequency range internal vibration peak; And

4. ultrasound piezoelectric transducer, it comprises the piezoelectric that is formed and is stretched, and takes this, the ultrasonic vibration at 10kHz-200kHz frequency range internal vibration peak can be launched and/or be received in to this transducer.

As follows to brief description of drawings:

Fig. 1 is the decomposition diagram of the ultrasound piezoelectric transducer of the present invention of band forming blocks and horizontal bar;

Fig. 2 detects the circuit block diagram of ultrasonic signal for using ultrasonic transducer of the present invention;

Fig. 3 launches the circuit block diagram of ultrasonic signal for using ultrasound piezoelectric transducer of the present invention;

Fig. 4 is the decomposition diagram of another ultrasound piezoelectric transducer of the present invention;

Fig. 5 summarily draws with the form of block diagram and is used to detect and launch the circuit of ultrasonic vibration;

Fig. 6 (a) and 6 (b) are respectively the front view and the end view of the forming blocks 13 among Fig. 1, Fig. 6 (a) garden cylindricality horizontal bar 14 that also draws;

Fig. 7 is the amplification optical projection figure of actual transducer chip shape;

Fig. 8 is the decomposition diagram with another ultrasound piezoelectric transducer of the present invention of forming blocks and horizontal bar;

Fig. 9 is the sectional view of piezoelectric among Fig. 1 or Fig. 8;

The sectional view of piezoelectric of Figure 10 for falling " U " shape;

Figure 11 (a) be a kind of piezoelectric sheet symmetric transverse pattern, by shown in the determined frequency diagram of angle θ, increase rapidly in about 20 degree place frequencies of corresponding " bending " pattern;

Figure 11 (b) is to the little number of degrees with greater than angle

θ draw pattern

1 and 3 of 20 degree;

Figure 11 (c) a kind of shape of a saddle one-way piezoelectric material that draws, the arrow of first figure among this figure illustrates the direction of motion;

Figure 11 (d) a kind of inverted U-shaped one-way piezoelectric material that draws, the arrow of first figure among this figure illustrates the direction of motion;

Figure 11 (e) is the piezoelectric length of Figure 11 (d) and the graph of relation of frequency;

The shape that employed piezoelectric among Figure 13-16 is drawn in Figure 12 (1), (2), (3) and (4);

Figure 13 (1)-(4) are for 1 * 2cm ²Single shaft is to the frequency of PVDF thin slice and power output relation curve (to the microphone response of shape (1)-(4) of Figure 12, output is uncorrected);

Figure 14 (1)-(4) are for 1 * 2cm ²The frequency of single transverse PVDF thin slice and power output relation curve (to the microphone response of shape (1)-(4) of Figure 12, output is uncorrected);

Figure 15 (1)-(4) are for 1 * 2cm ²The frequency of two-way PVDF thin slice and power output relation curve (to the microphone response of shape (1)-(4) of Figure 12, output is uncorrected); And

Figure 16 (1)-(3) are for 1 * 2cm ²The frequency of single transverse PVDF thin slice and power output relation curve (to the microphone response of shape (1)-(3) of Figure 12, output is uncorrected).

To describe below and constitute a kind of ultrasound piezoelectric transducer that is designed to be operated in about 100kHz frequency.The output of this transducer is higher (for working region 1cm ², the 10cm place is about 1Pa/V), and compare with other PZT (piezoelectric transducer), it has wide bandwidth (being about 30kHz between the 3dB).Receiving sensitivity depends on the type of the amplifier that is used for transducer, also depends on the noise (that is, using the high input impedance voltage amplifier can occur and low input impedance trsanscondutance amplifier characteristics inequality) of this system.

Referring to Fig. 1, the PVDF thin slice 10 with evaporation electrode 11 and 12 makes its bending on the forming blocks 13 with screw hole 25 (hole on the left side only is shown) by adjustable horizontal bar 14, and shown in Figure 1 as same figure, this horizontal bar is typically thin and hard wire rod.The size of piece 13 represents with respective symbol, be shown in Fig. 6 (a) and (b) in.For example be: L ₁=10.0, L ₂=14.5, H ₁=2.1, H ₂=1.5, S ₁=1.55, S ₂=3.45, S ₃=7.0, D=1.0, wherein unit is mm.The diameter of the bend 15 in the thin slice 10 is controlled by the height of the horizontal bar 14 that is positioned at piece 13 tops.Can influence operating frequency (being about 1cm when the 100kHz frequency) as sheet width 16, the diameter of bend 15 also influences operating frequency (being about 3mm when 100 frequencies).Their size also influences the amplitude (that is, transmitting and receiving sensitivity) of vibration.Thin slice 10 is by nylon screw 17 and 18 and be fastened on the piece 13 with the packing ring 21 of screw 18 couplings, and screw 17 and 18 also is used for making thin slice to contact with two terminals 19 and 20, and these terminals will contact with 12 with electrode 11 respectively.The part that approaches screw 17 and 18 of thin slice 10 can be handled with NaOH, and clearing up aluminium electrode 12 and 11 respectively, this will reduce the electric capacity that the working region with thin slice 10 is in parallel, and improves and receive and emission characteristics.

The most loud output frequency approaches to be expected at the standing wave resonance frequency above the thin slice 10, but because the effect of the resistance of the crooked shape that air or other gas are applied the thin slice 10 with low acoustic impedance can cause very strong resonance fuzzy.The holographic of vibration mode studies show that, the main motion vertical of thin slice in thin slice 10 and between the top of bend 15 middle parts and two bends 22 and 23 middle part.Fig. 7 amplification optical projection figure of actual transducer chip shape that draws.Label corresponding to Fig. 1 is added among Fig. 7, to be easy to quick comparison.All do not have appreciable conventional motion in any point at edge, do not have such motion on the center line below horizontal bar 14 yet.Therefore, for stopping the main motion of thin slice 10, can with support column 26 and 27 and 28 and 29 sheet support be got up respectively in the top of bend 22 and 23, as shown in Figure 1, perhaps this thin slice can with horizontal bar 14 tight closings, these modes all do not have illeffects.Except the width of cloth was penetrated face 22 and 23, the whole energy transducer of Fig. 1 all shielded with conductor, to reduce electromagnetism and acoustic jamming.The height of horizontal bar 14 can be adjusted (coming mobile forming blocks 13 with respect to the pedestal that supports horizontal bar 14) by screw, or adjusts (utilizing the frictional force between the hole on horizontal bar 14 and the forming blocks to make its location also finally by tightly closing) with hand simply.These two kinds of methods all only need a few times in second, and make parts simple, and whole assembly can be produced cheaply.

With similar shown in Fig. 1 but vicissitudinous structure is shown in Fig. 8.In this back one structure, PVDF thin slice 10a with evaporation electrode 11a and 12a (is generally 22 μ m-25 μ m, be typically 25 μ m) make its bending on the plastic shaping piece 13a that protuberance 25a (left side only is shown) all arranged on two faces by scalable horizontal bar 14a, this horizontal bar is typically the thin and hard wire rod that is with plastic sheath, and is shown in Figure 8 as same figure.The size of piece 13 is that unit is at Fig. 6 (a) with (b) with mm.The diameter of the bend 15a of thin slice 10a is controlled by the height of the horizontal bar 14a that is positioned at piece 13a top.The sheet width that is close as the width 16a with piece 13a can influence operating frequency (being about 1cm in the 100kHz frequency), and the diameter of bend 15a also influences operating frequency (being about 3mm at 100kHz).These two sizes also influence the amplitude (that is, transmitting and receiving sensitivity) of vibration.By hole 30a (left side only is shown) being enclosed within protuberance 25a (the right only is shown), thin slice 10a is fixed on piece 13a, and, thin slice 10a is contacted with two terminals 19a and 20a by plastic washer 21a and 21aa are placed on the protuberance 25a.Thin slice 10a can fix on protuberance 25 a it by the mode that claw is fixed on packing ring 21a and the 21aa.

For stopping the main motion of thin slice 10a, can distinguish nationality support column 26a and 27a and 28a and 29a, on the edge at bend 22a and 23a top, it is supported, as shown in Figure 8.Forming blocks 13a is preferably by insulator and constitutes.The height of horizontal bar 14a can save with hand adjustment, the time in this need several seconds, and make parts simple, whole assembly can be produced cheaply.

Piezoelectric 10 among Fig. 1 or Fig. 8 or 10a are the shapes of a saddle as shown in Figure 9, wherein, d2 is the diameter of section of horizontal bar 14 or 14a, it works with this piezoelectric with matching, with with its stretching, point A and C are the strong point of piezoelectric, x was the some A of some B and the piezoelectric shape length between the C, d1 is the distance between an A and the C, d3 is the distance between the saddle top, h1 is the height from the on line of an A and C to the piezoelectric at saddle top, left-hand side, hr is the height from the piezoelectric that links to right-hand side saddle top of an A and C, h21 is the saddle-shaped height in piezoelectric left-hand side, and h2r is the saddle-shaped height of piezoelectric right-hand side, wherein:

d1＝10mm；x＝20mm；hr＝7.5mm；

h1＝7.5mm；h21＝1.5mm；h2r＝1.5mm；

d2＝1.0mm；d3＝6.9mm

The another kind structure of ultrasound piezoelectric material is described below.

Referring to Fig. 4, adjustable excellent 104 bendings of PVDF thin slice 100 nationalitys with

evaporation electrode

101 and 102 are on the garden of alclad cylindrical plastic forming blocks 103, and shown in Figure 4 as same figure, this rod is typically thin and hard wire rod.The degree of crook of thin slice 100 is controlled by the height that is positioned at the rod 104 on piece 103 pedestals 114.Diameter 106 as thin slice can influence operating frequency, and the degree of crook of thin slice 100 is also influential to it.The two size also influences the amplitude (that is, transmitting and receiving sensitivity) of

vibration.By nylon screw

107 and 108 and with the packing ring 111 of screw 108 couplings, thin slice 100 is fastened to above the piece 103,

screw

107 and 108 also is used to make it to contact with 110 with two terminals 109, this contacts them respectively with electrode 101 and 102.The position available hydrogen sodium oxide molybdena that approaches

screw

107 and 108 of thin slice is handled, to clear up

aluminium electrode

102 and 101 respectively.This can reduce the electric capacity that is in parallel with thin slice 100 working regions, thereby improves reception and emission characteristics.

In order to stop the main motion on the thin slice 100, can not have of the support of any illeffects ground, or itself and rod 104 tight closings are realized by 113 pairs of edges 112, edge.Forming blocks 103 is preferably by insulator is rolling and forms, and whole element is comparatively ideal to be to shield with aluminium conductor, to reduce electromagnetism and acoustic jamming.The height of rod 104 can be regulated with screw (with respect to the pedestal that is used for fixing support stick 104, mobile forming blocks 103), perhaps regulate (utilizing the frictional force between the hole on rod 104 and the forming blocks to make its location) with hand simply also finally by tight closing.

Fig. 2 summarily draws with the form of block diagram and is used to detect the system 300 of ultrasonic vibration.The ultrasound piezoelectric transducer 301 that system 300 contains Fig. 1, Fig. 8 or Fig. 4 is made the amplifier 302 that electric property is connected with it.Amplifier 302 is also made electric property with filter 303 and is connected, and this filter 303 is made electric property with cathode-ray oscilloscope 304 again and is connected.

In use, system 300 is placed in the atmospheric environment that ultrasonic wave need detect.Ultrasonic vibration in air or other gas causes that transducer 301 makes ultrasonic vibration, and is changed into ultrasonic electrical signal by it.Ultrasonic electrical signal is amplified by amplifier 302, by filter 303 filtering and be displayed on the cathode-ray oscilloscope 304.

Fig. 3 summarily draws with the form of block diagram and is used to launch the system 400 of ultrasonic vibration.System 400 contains ultrasound piezoelectric transducer 401 and ultrasonic wave rectangle/sine-wave generator 402 or the ultrasonic pulse generator 403 of Fig. 1, Fig. 8 or Fig. 4, and it is made electric property with transducer 401 and is connected.

In use, system 400 is positioned in the atmospheric environment that ultrasonic wave need launch.By rectangle/sine-wave generator 402 or pulse generator 403 ultrasonic electrical signal is added on the transducer 401, makes transducer 401 do the vibration of ultrasonic rolling land, thereby ultrasonic vibration is transmitted in ambient air or other gas.

Fig. 5 summarily draws with the form of block diagram and is used to detect and launch the system 500 of ultrasonic vibration, the ultrasound piezoelectric transducer 501 that system 500 contains Fig. 1, Fig. 8 or Fig. 4 with make the amplifier 502 that electric property is connected by switch 505 and transducer 501.Amplifier 502 is made electric property with filter 503 again and is connected, this filter and make electric property with cathode-ray oscilloscope 504 and be connected.System 500 contains ultrasonic wave rectangle/sine-wave generator 506 or ultrasonic pulse generator 507, and it is made electric property by switch 505 and transducer 501 and is connected.

In use, system 500 is positioned in and needs in the detected atmospheric environment of ultrasonic wave.Ultrasonic vibration in air or other gas causes that transducer 501 does the vibration of ultrasonic rolling land, and converts ultrasonic electrical signal to by transducer 501.This signal of telecommunication is sent to amplifier 502 by switch 505, and when system was in detecting pattern, this switch was connected transducer 501 with amplifier 502.Ultrasonic electrical signal is exaggerated device 502 and amplifies, and filtered device 503 filtering also are displayed on the oscilloscope 504.At emission mode, the ultrasonic electrical signal of rectangle/sine-wave generator 506 or pulse generator 507 is added on the transducer 501 by switch 505, this switch is connected with generator 506 or 507, this ultrasonic electrical signal causes that transducer 501 does the vibration of ultrasonic rolling land, thereby cause that ultrasonic vibration is launched among ambient air or other gas, vibration can be passed to above the reflecting surface 508, from this reflecting surface, they are reflected, and are detected by system 500 in detecting pattern.

Two systems 500 (its each have as top Fig. 1 that has just described, Fig. 8 or Fig. 4 transducer) can be positioned in mutually at a distance of the position of certain distance, and alternately transmit and receive ultrasonic signal, to carry out the measurement such as flow rate of gas.Another kind has the system 500 of two transducers (its each all be according to Fig. 1, Fig. 8 or Fig. 4 transducer), two transducers are placed also at a distance of certain distance ground mutually and are are alternately transmitted and received ultrasonic signal, to carry out the measurement such as flow rate of gas.

Example 1

As noted above, piezoelectric of the present invention has the curved shape that contains a flex point, and be envisioned for this curved shape and also have the suitable width of cloth and penetrate geometry, this will cause piezoelectric excitation to be coupled as lateral displacement effectively, take this, and the transverse vibration of out of phase is interfered longways mutually and produced high power output, when this situation takes place, then transducer promptly, produces the surface vibration that parallels with piezoelectric material surface in the excitation of fiducial axis to/expansion mode.The effect of transducer curved shape of the present invention can be summed up as three aspects:

1. when length resonance was used, resonance frequency increased with the increase of curvature, its value relevant with the total curvature along thin slice (Figure 11 (a)).

2. when whole length of thin slice are encouraged by same-phase ground, as common situation, comprehensive curvature will cause the lateral displacement response that interrelates with axial expansion to be distribution brokenly along thin slice, and maximum displacement is corresponding to the point of maximum curvature.On each flex point of thin slice curve, the phase overturn of displacement (in no flex point but curvature when very big, phase overturn also can take place, shown in Figure 11 (b)).

3. Wan Qu thin slice is the transducer that the width of cloth is penetrated shape.

It is 25 μ m that Figure 11 (c) is used for carrying out that gas velocity is measured, its thickness in local gas with one, and the PVDF piezoelectric that about 10mm is wide, 20-30mm grows illustrates these comprehensive features.Employed best thin slice is unidirectional thin slice, and cut with the direction of motion that bar shaped intersects on its edge, because this will suppress the strong extension pattern (yet two-way PVDF also may be utilized) that length direction exists.If this pattern exists, it will produce another response peak below needed peak, and will cause the low frequency fluctuation of output.This thin slice is energized on the broad ways being positioned at and being lower than on the frequency of first frequency range response.This vibration is by corresponding cycle expansion along thin slice of Poisson coupling (Poisson coupling) generation of forced, and it all is a homophase at every place.By to the fixing of every end with across the hold-down bars at its middle part, the shape shown in this thin slice is bent to, this formation is about effective width of cloth of 100mm2 and penetrates the district.The pier shape of two deep cambers has the transverse movement of enhancing and is homophase.Low ebb between them, transverse vibration are anti-phase.The whole shape of irradiator forms total output, and it produces about 100kHz wavelength is the strong broadband response of 3mm.This response is strengthened by the frequency range resonance that is positioned at same frequency.

Second kind of structure is shown in Figure 11 (d), and it is applicable to the piezoelectric of the lower frequency of 20-50kHz.In this case, a unidirectional thin slice is cut along the direction of motion, and is used as the basis of piezoelectric along the strong extension resonance of thin slice.This thin slice is fixed becomes to be simple " U " shape, and the bent front ends portion of " U " shape flattens it a little with a hold-down bars.When this thin slice is extruded, and this width of cloth will obtain best output when penetrating face and just approaching the plane.At that point, to penetrate the vibration of face be homophase to the whole width of cloth.If this thin slice is adjusted very flatly on a zone of centre, will produce antiphase, this will cause the loss of response.Operating frequency depends primarily on sheet length, and next depends on final curved shape, and it the results are shown in Figure 11 (e).Second effect of hold-down bars is the broadening frequency response.

Example 2

The theory of sound propagation of material is normally based on the continuity of ripple.Yet the typical thickness of piezoelectric plastic film is the 10-100 micron, and it is more much smaller than the wavelength of propagating on film, so continuity theory is inapplicable herein.The research of the theory of sound propagation in film is therefore and complicated and only can finish with approximate method, but allow with fiducial axis to or expansion wave be equal to mutually, these ripples are main apparent motions that produce and parallel with film surface ripple and lateral wave.These ripples can resemble not rotation wave or indiffusion Poona sample occurs, and also can resemble to occur bulk wave or the surface wave.[“Structure-Borne?Sound”，Cremer，Heckl，Heckl&Ungar，Springer-Verlag，Berlin，1973]。

Below to cut into 10 * 20mm thickness be 25 μ m the PVDF film experiment shows the influence of thin slice physical dimension to interacting between expansion wave and the lateral wave and propagating.To the unidirectional PVDF thin slice that forms with axially parallel or perpendicular cuts, the peak on the spectrum that further comparison shows that mutually of its propagation spectrum depends on axial or horizontal ripple.

(all thin slices are 1 * 2cm) to have contrasted to be shown in flake structure among Figure 12, that be denoted as (1), (2), (3) and (4) to four kinds.

Figure 13-Figure 16 of PVDF flake structure (1)-(4) of horizontal wide 1cm has proved the transfer of energy between each pattern, and shows the best relevant with current piezoelectric and critical shape.

Use the term of Fig. 9, total length x partly determines frequency, and h2 and length ratio are determined frequency and output.

H21 and h2r ± variation of 0.5mm allows, but therefore can produce decline fast in output, for example ± and 1.0mm causes that signal reduces by 4 times.

Electrode substance to the influence of transducer output is: the molecular wt/density of thin slice is high more and thickness of electrode is thick more, and then the output of transducer and Oscillation Amplitude are low more, for example arranges from Al-Ti-Ag-Au, will produce gradually low on the dB value of output.

Example 3

To the diameter of type shown in Figure 4 is that the circular piezoelectric material of 20mm has carried out main test.Compare with the transducer of Fig. 1 or type shown in Figure 8, the low 10dB of its output, but this does not count the caused invalid bending of insufficient moulding of plastics in the mould.

Ultrasound piezoelectric transducer of the present invention is specially adapted in air or other gas or liquid to detect and/or the system of emission ultrasonic vibration, and that these other gases comprise is civilian, at the gas of the industrial use of commercial one-tenth, and liquid comprises water and seawater.

Claims

1. the PZT (piezoelectric transducer) that can transmit and receive ultrasonic vibration comprises the piezoelectric sheet of working with the device of the support and the described thin slice that stretches with matching, wherein:

Described thin slice is shaped by described device and stretches, and to form a shape of a saddle thin slice with three sweeps, wherein the sweep that is adjacent of each described sweep has opposite sign of curvature, and is not fixed on the described device, and

Described thin slice is not restrained between each described part, and is supported on the described device by the arbitrary limit in the both sides of described saddle-shaped three sweeps.

2. transducer as claimed in claim 1, wherein said ultrasonic vibration has the vibration peak in the 10KHz-200KHz frequency range.

3. transducer as claimed in claim 1, the device of the wherein said support and the described thin slice that stretches comprises in three sweeps with described shape of a saddle thin slice two, and work is to support the support column of described two parts with matching, and described two parts have identical sign of curvature.

4. transducer as claimed in claim 1, wherein said device comprises the back-up block that described thin slice is placed on it, work is to support the support column of described two parts with matching in described three sweep that have with described shape of a saddle thin slice two, and described two parts have identical sign of curvature.

5. transducer as claimed in claim 3, wherein said support column are wedge shape.

6. transducer as claimed in claim 4, wherein said support column are wedge shape.

7. transducer as claimed in claim 2, the device of the wherein said support and the described thin slice that stretches comprise one with one of sweep of the described shape of a saddle thin slice work is with the stretching rod of one of the described sweep that stretches with matching, two sweeps of this sweep and other have opposite sign of curvature.

8. transducer as claimed in claim 3, the device of the wherein said support and the described thin slice that stretches comprise one with one of sweep of the described shape of a saddle thin slice work is with the stretching rod of one of the described sweep that stretches with matching, two sweeps of this sweep and other have opposite sign of curvature.

9. transducer as claimed in claim 7, wherein

1.5 ^*d ₁≤x≤2.3 ^*d ₁；

0.5 ^*d ₁≤h _r≤0.9 ^*d ₁；

0.5 ^*d ₁≤h ₁≤0.9 ^*d ₁；

0.1 ^*d ₁≤h ₂₁≤0.2 ^*d ₁；

0.1 ^*d ₁≤h _2r≤0.2 ^*d ₁；

0.05 ^*d ₁≤d ₂≤0.2 ^*d ₁；

0.6 ^*d ₁≤d ₃≤0.8 ^*d ₁.

d ₂Be the diameter in the cross section of described stretching rod, some A and C are the described strong points at piezoelectric sheet, and x was the some A of some B and the material shape length of the described piezoelectric sheet between the C, d ₁Be the distance between an A and the C, d ₃Be the distance between the top of described two sweeps, h ₁Be height from the piezoelectric sheet at the top of the left-hand side sweep of described two sweeps of linking to of an A and C, h _rBe height from the piezoelectric sheet at the top of the right-hand side sweep of described two sweeps of linking to of an A and C, h ₂₁Be the height of the left-hand side sweep of described two sweeps, h _2rIt is the height of the right-hand side sweep of described two sweeps.

10. transducer as claimed in claim 8, wherein

1.5 ^*d ₁≤x≤2.3 ^*d ₁；

0.5 ^*d ₁≤h _r≤0.9 ^*d ₁；

0.5 ^*d ₁≤h ₁≤0.9 ^*d ₁；

0.1 ^*d ₁≤h ₂₁≤0.2 ^*d ₁；

0.1 ^*d ₁≤h _2r≤0.2 ^*d ₁；

0.05 ^*d ₁≤d ₂≤0.2 ^*d ₁；

0.6 ^*d ₁≤d ₃≤0.8 ^*d ₁

11. transducer as claimed in claim 9, wherein:

d ₁＝10mm；

x＝20mm；

h _r＝7.5mm；

h ₁＝7.5mm；

h ₂₁＝1.5mm；

h _2r＝1.5mm；

d ₂＝1.0mm；

d ₃＝6.9mm.

12. as any one transducer in the claim of front, wherein said thin slice is a kind of polyvinylene based polyalcohol (polyvinylidene polymer) or a kind of vinylidene fluoride of connection and copolymer of trifluoro-ethylene of connection.

13. as the transducer of claim 12, wherein said thin slice is a kind of polyvinylene polymer flake of connection.

14. as the transducer of claim 13, wherein said thin slice is a kind of polyvinylene polymer flake of connection, its thickness is 9 μ m-35 μ m.

15. as the transducer of claim 14, wherein said thin slice is a kind of polyvinylene polymer flake of connection, its thickness is 25 μ m.

16. as any one transducer among the claim 1-11, the width 1mm-500mm of wherein said thin slice.

17. as the transducer of claim 16, the width of wherein said thin slice is 5mm-20mm.

18. as the transducer of claim 17, the width 10mm of wherein said thin slice.

19. as any one transducer among the claim 1-11, wherein said ultrasonic vibration has the vibration peak in the 80KHz-120KHz frequency range.

20. as any one transducer among the claim 1-11, the vibration peak in the wherein said ultrasonic vibration tool 15KHz-60KHz frequency range.

21. as the transducer of claim 20, wherein said ultrasonic vibration has the vibration peak in the 15KHz-30KHz frequency range.