GB2212695A - Piezoelectric transducer element - Google Patents
Piezoelectric transducer element Download PDFInfo
- Publication number
- GB2212695A GB2212695A GB8826752A GB8826752A GB2212695A GB 2212695 A GB2212695 A GB 2212695A GB 8826752 A GB8826752 A GB 8826752A GB 8826752 A GB8826752 A GB 8826752A GB 2212695 A GB2212695 A GB 2212695A
- Authority
- GB
- United Kingdom
- Prior art keywords
- transducer
- casing
- transducer element
- polarization
- element according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000010287 polarization Effects 0.000 claims description 22
- 229910052751 metal Inorganic materials 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 7
- 229920003023 plastic Polymers 0.000 claims description 5
- 239000006260 foam Substances 0.000 claims description 4
- 239000004033 plastic Substances 0.000 claims description 4
- 229920002635 polyurethane Polymers 0.000 claims description 3
- 239000004814 polyurethane Substances 0.000 claims description 3
- 229910000831 Steel Inorganic materials 0.000 claims description 2
- 239000010959 steel Substances 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 230000000644 propagated effect Effects 0.000 description 5
- 238000010276 construction Methods 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 3
- 230000008602 contraction Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- -1 etc. Substances 0.000 description 3
- 238000010008 shearing Methods 0.000 description 3
- 239000011345 viscous material Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 229920001971 elastomer Polymers 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000005060 rubber Substances 0.000 description 2
- 230000011664 signaling Effects 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 238000004026 adhesive bonding Methods 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 description 1
- 229910002113 barium titanate Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000002305 electric material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000012858 resilient material Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000003190 viscoelastic substance Substances 0.000 description 1
Classifications
-
- 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
- G10K11/002—Devices for damping, suppressing, obstructing or conducting sound in acoustic devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
- B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
- B06B1/0662—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface
- B06B1/0681—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface and a damping structure
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Mechanical Engineering (AREA)
- Transducers For Ultrasonic Waves (AREA)
- Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
Description
1 v A' B&S No C88/65 1 - TRANSDUCER ELEMENT r 221269 J The invention
relates to a transducer element, more particularly a hydrophone for extended transducer arrangements of the kind specified in the preamble of claim 1.
Such transducer elements have a piezo element having a direction of polarization such that its piezo-electric reception properties 0 mainly become operative for acoustic pressure from a single direction.
If in the case of a transducer element the acoustic pressure acts on a piezo-electric element on all sides, the piezo effect produces an electric output voltage of the transducer element. The output voltage is mainly caused by the acoustic pressure operative in the direction of polarization of the transducer element, and therefore only that portion of the output voltage which is generated by this component of the acoustic pressure should be described as the wanted signal of the transducer element. In general the acoustic pressure operative substantially transversely thereof is regarded as noise which generates, since it is transverse of the direction of polarization, an output voltage smaller by orders of magnitude, i.e., the spurious or noise signal. The signal-to-noise ratio (SNR) as the quotient of the wanted and spurious signals characterizes the quality of the transducer element.
2 Transducer elements of the kind specified are used as hydrophones in transducer arrangements in underwater sonic technology to receive sound waves of selective direction and to locate targets radiating acoustic signals. Sensitivity to noise waves and therefore a reduced SNR is a considerable disadvantage to the detection properties of such a hydrophone.
It is an object of the invention to provide a transducer element which is adapted in an optimum manner to the acoustic pressure to be absorbed in the direction of polarization of the piezo element and which is insensitive to sound waves propagated transversely of the direction of polarization.
This problem is solved according to the invention in a transducer element of the kind set forth in the preamble of claim 1 by the features of the characterizing part thereof.
Noise waves are essentially generated in the form of flexural waves which have a very much smaller wave length than the wave length of sound and which are propagated longitudinally of the vessel, for example, along hull walls and therefore also along the longitudinal antennas mounted thereon.
The advantage of the transducer element according to the invention is that the steps according to the invention prevent the lateral surfaces of the piezo element from being excited by the noise waves. The casing performs two functions; on the one hand it mechanically and spatially separates the lateral surfaces of the piezo element from the propagation medium and on the other i 4 T 1.
3 it prevents noise waves from impinging on the lateral surfaces either by reflecting or absorbing the noise as completely as possible, or by a combination of partial reflection and partial absorption. If the casing moreover is made at least partially from a resilient or elastic-viscous material, due to the wanted sound the piezo element can perform free volumetric oscillations which are not radiated beyond the casing into the propagation medium. 1 An advantageous further development of the invention can also be gathered from claim 2, because if the acoustic impedance of the casing substantially differs from the internal impedance of the noise source for the noise waves impinging transversely of the direction of polarization - e.g., by at least one order of magnitude, i.e., at least 10:1 or even 100:1 and more the noise waves are reflected at the boundary layer of the materials, the external surface of the casing, in dependence on the reflection factor determinable from the impedances. Since the reflection factor is proportional to the differences between the impedances, both possibilities - i.e., of making the impedance of the casing substantially higher or substantially lower than the impedance of the noise source - can be used in the same advantageous manner.
An advantageous further development of the invention as set forth in claim 5 results in the construction of a light-weight transducer element which can also be produced in a particularly simple manner by suitably foaming resilient or elastic-viscous material or syntactic foam.
- 4 An advantageous further feature of the invention set forth in claim 6 produces a heavy construction of the transducer element which can advantageously be used more particularly in relation to acoustic signals mainly propagated by their velocity component such as, for example, flexural waves, since transducers insensitive to sound velocity must be constructed with a heavy weight, so as not to be moved - i.e., excited by the velocity component.
For all sound waves impinging transversely of the direction of the useful sound, the metal layer constructed in the form of a steel ring is a reflector having an impedance which is increased as against the characteristic impedance of water and is in general ill-adapted to the noise source. Unreflected residual signal components are absorbed via the intermediate layer provided between the metal layer and the piezo element.
The resilient intermediate layer also has the advantage that the piezo element can still oscillate freely, so that any shearing force expansion occurring transversely thereof due to contraction in the direction of polarization can pass unimpeded into the resilient intermediate layer.
Another advantage can also be gathered from claim 7. Since it has an encapsulating envelope of sound-transparent recast material, the transducer element is not in direct contact with the propagation medium for the noise, in general water. As a result, the noise waves propagated with a particularly high velocity component cannot act directly on the transducer element.
1..
The invention will now be described in greater detail with reference to an embodiment thereof, wherein:
Fig. la shows a transducer element having a casing including microbubbles, Fig. 1b shows a transducer element having a two-layer casing, Fig. 2 is a cross-section through a transducer arrangement having a single transducer element, and Fig. 3 is a cross-section through a transducer arrangement having a number of transducer elements.
Fig. la shows a transducer element 10.1 according to the invention in its basic structure. The transducer element 10.1 comprises a piezo element 11 enclosed by a casing 12. The piezo electric material used for the piezo element 11 illustrated is a piezo electric ceramic, such as barium titanate, which has an acoustic impedance as similar as possible to the characteristic impedance of water. However. the piezo element might also be built up from piezo electric foil, such as PVDF, etc., or layers of foils.
The casing 12 is made of a resilient or elastic-viscous material, such as syntactic foam, plastics or rubber, in which microbubbles 13 have been produced during the manufacturing process. The microbubbles are present on the external surfaces in increased concentration. The impedance of the casing 12 is very essentially determined by the gas-filled microbubbles 13 and is therefore substantially lower than that of its sound-transparent plastics. As a result, the casing 12 reflects incident noise waves due to the impedance jump produced by the microbubbles 13 between the sound propagation medium and the casing 12. The elastic-viscous plastics is in itself.sound- asborbing - i.e., damping - so that the unreflected sound wave components penetrating the casing 12 are further damped and the lateral surfaces of the piezo element are no longer excited by spurious signal components.
The transducer element 10.1 is cylindrical, and the direction of polarization of the piezo element 11 coincides with its axis 16, shown by a chain-dot line. Signalling lines 15 are connected to electrically conductive coatings 14.1 and 14.2.
Fig. lb shows another transducer element 10.2. Like constructional elements to those of the transducer element 10.1 in Fig. la have like references. In the transducer element 10.2 the piezo element 11 has a casing 12 consisting of two layers of material, a metal layer 12.1 and an intermediate layer 12.2. The intermediate layer 12.2 is sound-transparent and made of a resilient or visco-elastic material, such as synthetic foam, plastics or rubber.
The transducer element 10.2 is also of axially symmetrical construction and its operative piezo element 11 is so polarized that its direction of polarization coincides with the axis of symmetry 16 shown by a chain-dot line. The metal layer 12.1 then A forms a ring around the cylindrical piezo element 11. The oscillating piezo element 11 can be satisfactorily mechanically attached in a very simple manner by glueing the annular metal layer 12.1 to the intermediate layer 12.2 andthe intermediate layer 12.2 to the piezo element 11, unless the adhesive forces of the intermediate layer 12.2 themselves ensure adequate mechanical firmness.
In Fig. lb the direction of propagation of the wanted sound is shown by arrow 17, the direction of propagation of the noise being shown by arrow. 18. The piezo element 11 contracts in the direction of polarization 16 and expands transversely thereof as a result of the sound pressure of the wanted sound, which impinges unimpeded on the piezo element 11 in the direction of the axis of symmetry 16. The differential voltages produced by piezo effect on the coatings 14.1 and 14.2 are delivered via the electric lines 15 to connected signal processing circuits (not shown). The ceramic can oscillate unimpeded inside the transducer element 10.2, since in the case of contraction in the direction of polarization the resilient intermediate layer does not impede any expansion occurring transversely thereof due to the shearing stresses. In contrast, the rigid metal layer 12.1 prevents any further propagation of the waves of shearing stress, for example, to adjacent transducer elements. As against this, noise impinging on the transducer element 10 transversely of the direction of polarization 16 is reflected on the reverberant casing 12 and exerts no pressure on the piezo element 11. This prevents any transverse contractions which a piezo-electric signal might produce, although to a substantially lesser extent.
Since the impedance of the piezo element 11 is substantially adapted to the characteristic impedance of water and the wanted sound pressure is generated by a sound source whose inner impedance is equal to the impedance of water -PO.CO m 1.5.106Ns/m3 there is an adaptation of power in the direction of polarization 16 as between the water and the transducer element 10, and a maximum power transition can take place, the casing 12 having no effect in the direction of polarization 16.
Transversely of the direction of polarization 16, in the direction of propagation 18 of the noise, either the impedance of the casing 12 is illadapted to that of the water or water-like enveloping materials, for example, polyurethane, of the incorporated transducer element 10, or the noise is propagated substantially as a sound velocity component - i.e., it is generated by a source of lower impedance than that of water (Z%O.l., p C to 0.01.P C), so that no power transition takes 0 0 j 1 0 0 place from the water or enveloping material to the casing 12. In every respect the transducer element 10 is ill-adapted to the noise source and remains inoperative for influencing the piezo ceramics 11. As a result of its construction, therefore, the transducer element 10 is of optimum design as regards its signal transmitting properties for the different propagation properties of noise and wanted sound.
The sectional drawings in Figs. 2 and 3 illustrate the basic incorporation in extended transducer arrangements 22, 22' of 1 A transducer elements 10, which in the embodiment illustrated are constructed like the transducer elements 10.2 described in connection with Fig. lb. The extended transducer arrangement 22, 22', frequently known as a flank array system (FAS) or longitudinal antenna, is mounted by means of an attaching element 21, 21' on a vertical hull wall 20, 20' in the direction of the longitudinal axis of a vessel, for example, a submarine. Each of the transducer elements 10 is fixed in its position, whose spacing is small in relation to the coherency wave length of the noise, in a sheathing body 23, 23' by the casting-around of an envelope 24, 24' of a material, for example, polyurethane, which gives adequate support mechanically but is acoustically transparent. The signalling lines 15 of all the transducer elements 10 of the arrangement 22, 22' are combined in a joint cable.25, 25'.
The transducer arrangement 22' shown in Fig. 3 differs from the arrangement 22 shown in Fig. 2 merely by the feature that a number of transducer elements 10 are cast in at one position. In the embodiment illustrated in Fig. 3, three transducer elements 10 are fixed by casting with an angular offsetting of approximately 600 at the outer edge. In both embodiments (Figs. 2 and 3) the directions of polarization 16 are transverse of the vessel longitudinal axis, which in this case extends perpendicularly through the plane of the drawing - i.e., tranversely of the direction of propagation of the noise.
- 10
Claims (10)
1. A transducer element, more particularly a hydrophone for extended transducer arrangements, having a piezo element of given direction of polarization, wherein the piezo element has a casing covering its lateral surfaces extending parallel with the direction of polarization; the piezo element and the casing are so mechanically interconnected that the piezo element is acoustically uncoupled at least from the external surfaces of the casing; and the casing is constructed to reflect and/or absorb the sound of noise waves impinging transversely of the direction of polarization.
2. A transducer element according claim 1, wherein the acoustic impedance of the casing differs substantially from the internal impedance of the noise sources by at least one order of magnitude for noise waves impinging transversely oil the direction of polarization.
A transducer element according to claim 1 or claim 2, wherein the piezo element and the casing are concentric cylinders, and the direction of polarization coincides with the direction of the cylinder axis.
4. A transducer element according to any preceding claim, wherein the piezo element is glued to the casing.
5. A transducer element according to any preceding claim, wherein the casing is made of a synthetic foam or a resilient or visco-elastic plastics with gas-filled microbubbles, the microbubbles being preferably concentrated on the external surfaces.
1 i;P 0 A - 11
6. A transducer element according to any preceding claim, wherein the casing consists of a reverberant metal layer, preferably a steel ring, and a resilient or elastic-viscous intermediate layer disposed between the metal layer and the piezo element.
7. A transducer element according to any preceding claim, wherein its envelope is made of sound-transparent recast material, preferably polyurethane.
8. A transducer element according to any preceding claim, which is so positioned in an extended transducer arrangement that the direction of polarization is perpendicular to the longitudinal axis of the transducer arrangement, one or more transducer elements being provided at the same position in the transducer arrangement.
9. A transducer element according to any preceding claim, which is positioned in the transducer arrangement at a distance from an adjacent transducer element which is small in comparison with the coherency wave length of the noise.
10. A transducer element substantially as herein described and shown in the accompanying drawings.
Published 1989 atThe Patent Office, State House, 66,171 High Holborn, LondonWClR4TP.FIurther copies may be obtained from The Patent Office. Sales Branch, St Mary Cray, Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray. Kent, Con. TJ8,7
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19873739185 DE3739185A1 (en) | 1987-11-19 | 1987-11-19 | CONVERTER ELEMENT |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8826752D0 GB8826752D0 (en) | 1988-12-21 |
| GB2212695A true GB2212695A (en) | 1989-07-26 |
Family
ID=6340785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8826752A Withdrawn GB2212695A (en) | 1987-11-19 | 1988-11-16 | Piezoelectric transducer element |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE3739185A1 (en) |
| FR (1) | FR2623683A1 (en) |
| GB (1) | GB2212695A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2272818A (en) * | 1992-11-19 | 1994-05-25 | Flow Research Evaluation Diagn | Sonar transducers |
| US7680000B2 (en) | 2004-08-05 | 2010-03-16 | Atlas Elektronik Gmbh | Method for production of an antenna section for an underwater antenna |
| WO2016162008A1 (en) * | 2015-04-09 | 2016-10-13 | Atlas Elektronik Gmbh | Transducer device, transducer apparatus, sonar and water craft |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4140040A1 (en) * | 1991-12-05 | 1993-06-09 | Robert Bosch Gmbh, 7000 Stuttgart, De | ULTRASONIC DAMPING MATERIAL |
| DE10119867B4 (en) | 2001-04-24 | 2005-10-13 | Atlas Elektronik Gmbh | Underwater antenna |
| DE102006008718B4 (en) * | 2006-02-24 | 2017-05-18 | Volkswagen Ag | Ultrasonic sensor module |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1241131A (en) * | 1968-05-10 | 1971-07-28 | Krupp Gmbh | Electro-acoustic transducer |
| GB1454844A (en) * | 1973-03-27 | 1976-11-03 | Inst Francais Du Petrole | Pressure sensor |
| GB1518592A (en) * | 1975-04-24 | 1978-07-19 | France Armed Forces | Emitting or picking up an acoustic signal by means of a piezoelectric transducer |
| GB1551004A (en) * | 1976-04-22 | 1979-08-22 | British Petroleum Co | Hydrophones |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB157229A (en) * | 1914-12-10 | 1922-02-23 | Signal Gmbh | Submarine sound receiving plant |
| GB735319A (en) * | 1952-10-14 | 1955-08-17 | Clevite Corp | Disk transducer |
| US3359537A (en) * | 1964-06-30 | 1967-12-19 | Westinghouse Electric Corp | Transducer |
| FR2603761B1 (en) * | 1982-06-22 | 1989-01-13 | France Etat Armement | SONAR ANTENNA CONSTITUTING THE REPORTED HEAD OF AN UNDERWATER AND METHOD OF MANUFACTURE |
| GB8432508D0 (en) * | 1984-12-21 | 1985-02-06 | Avtaec Ltd | Underwater transducers |
-
1987
- 1987-11-19 DE DE19873739185 patent/DE3739185A1/en not_active Withdrawn
-
1988
- 1988-11-16 GB GB8826752A patent/GB2212695A/en not_active Withdrawn
- 1988-11-17 FR FR8814950A patent/FR2623683A1/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1241131A (en) * | 1968-05-10 | 1971-07-28 | Krupp Gmbh | Electro-acoustic transducer |
| GB1454844A (en) * | 1973-03-27 | 1976-11-03 | Inst Francais Du Petrole | Pressure sensor |
| GB1518592A (en) * | 1975-04-24 | 1978-07-19 | France Armed Forces | Emitting or picking up an acoustic signal by means of a piezoelectric transducer |
| GB1551004A (en) * | 1976-04-22 | 1979-08-22 | British Petroleum Co | Hydrophones |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2272818A (en) * | 1992-11-19 | 1994-05-25 | Flow Research Evaluation Diagn | Sonar transducers |
| US7680000B2 (en) | 2004-08-05 | 2010-03-16 | Atlas Elektronik Gmbh | Method for production of an antenna section for an underwater antenna |
| WO2016162008A1 (en) * | 2015-04-09 | 2016-10-13 | Atlas Elektronik Gmbh | Transducer device, transducer apparatus, sonar and water craft |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2623683A1 (en) | 1989-05-26 |
| GB8826752D0 (en) | 1988-12-21 |
| DE3739185A1 (en) | 1989-06-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |