GB2080613A - Piezoelectric transducer - Google Patents
Piezoelectric transducer Download PDFInfo
- Publication number
- GB2080613A GB2080613A GB8018036A GB8018036A GB2080613A GB 2080613 A GB2080613 A GB 2080613A GB 8018036 A GB8018036 A GB 8018036A GB 8018036 A GB8018036 A GB 8018036A GB 2080613 A GB2080613 A GB 2080613A
- Authority
- GB
- United Kingdom
- Prior art keywords
- membrane body
- membrane
- transducer
- unit
- piezoelectric transducer
- 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- Withdrawn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
- 239000012528 membrane Substances 0.000 claims abstract description 68
- 239000000463 material Substances 0.000 claims abstract description 11
- 239000004033 plastic Substances 0.000 claims abstract description 10
- 229920003023 plastic Polymers 0.000 claims abstract description 10
- 239000004743 Polypropylene Substances 0.000 claims description 3
- 239000004793 Polystyrene Substances 0.000 claims description 3
- 239000003822 epoxy resin Substances 0.000 claims description 3
- 229920000647 polyepoxide Polymers 0.000 claims description 3
- -1 polypropylene Polymers 0.000 claims description 3
- 229920001155 polypropylene Polymers 0.000 claims description 3
- 229920002223 polystyrene Polymers 0.000 claims description 3
- 239000004020 conductor Substances 0.000 claims description 2
- 239000012799 electrically-conductive coating Substances 0.000 claims 1
- 239000013078 crystal Substances 0.000 abstract description 19
- 239000011248 coating agent Substances 0.000 description 7
- 238000000576 coating method Methods 0.000 description 7
- 238000010276 construction Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 101100345589 Mus musculus Mical1 gene Proteins 0.000 description 1
- 208000036366 Sensation of pressure Diseases 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229920002457 flexible plastic Polymers 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000001465 metallisation Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R17/00—Piezoelectric transducers; Electrostrictive transducers
- H04R17/02—Microphones
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
- G01L9/008—Transmitting or indicating the displacement of flexible diaphragms using piezoelectric devices
-
- 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
- G10K13/00—Cones, diaphragms, or the like, for emitting or receiving sound in general
-
- 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
- G10K9/00—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers
- G10K9/12—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated
- G10K9/122—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated using piezoelectric driving means
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
- H10N30/302—Sensors
Abstract
An electric transducer unit having a membrane body (1) for sensing mechanical vibrations and a piezoelectric transducer (2), e.g. a crystal, coupled mechanically to the membrane body. The membrane body (1) is made of an elastic plastics material and the piezoelectric transducer (2) is located within the membrane body (1), whereby the transducer (2) is protected against external forces which may act on the outer surface of the membrane body (1). Terminal leads (3, 4) are connected to electroded surfaces of the crystal (2), or, in a form in which the membrane body (1) is made in two parts, one part may be of electrically conductive plastics material and serve as a terminal. The membrane body may be incorporated as part of a housing. <IMAGE>
Description
SPECIFICATION
Electric transducer unit for sensing mechanical
vibrations or other pressure changes
The invention relates to an electric transducer unit
for sensing mechanical vibrations or other pressure
changes, comprising a membrane for sensing press
ure changes and a piezoelectric transducer coupled
to the membrane. Such an electric transducer unit
can be used in piezoelectric transducers.
In recent years the application of piezoelectric
transducers comprising membranes for sensing
mechanical vibrations or other pressure changes has
become a conventional technique, and the mecha
nical connection between the membrane and the
crystal of the piezoelectric transducer can be solved
by many known ways. The basic principle of the
function of such a transducer lies in that in response
to the deformation of the piezoelectric crystal occur
ring under the effect of pressure changes applied on
the membrane an electrical voltage is generated that
is proportional to this deformation.
In one of the known piezoelectric transducers of
this kind the crystal is mounted on the inner surface
of the membrane e.g. by means of sticking or
soldering. Such a construction is described in detail
in Hungarian patent 160 565. In this patent the
problems connected with the different known solu
tions are also summarised. The transducer de
scribed in this patent is advantageous because the
whole deformation acting on the membrane is
directly transferred to the crystal without any cou
pling member therebetween, and thus the electric
sensitivity and the electrical transmission properties
of such a transducer are more favourable than that
of the prior constructions.
The adhesive or soldered connection between the
crystal and the membrane transfers all kinds of
forces acting on the membrane to the crystal. This
phenomenon, which is advantageous as far as
electrical properties are concerned, becomes dis
advantageous if external force effects substantially
exceeding the operational limit values act on the
membrane. Such force effects can occur if the
transducer is accidentally dropped or knocked
against a hard object. The crystal of the piezoelectric
transducer is a fragile and thin plate which can easily
be split or broken by such forces.
In addition to the dangers outlined above, it is very
difficult to achieve the required quality control of the
soldered connection and the danger of a possible disconnection can be avoided only by using a very
careful and disciplined manufacturing technology.
An object of the present invention is to provide an
electric transducer unit that is at least equal to other
known constructions as regards its electric prop
erties, but which is more advantageous as regards
its mechanical stability, its protection offered for the
crystal against external force effects, its life and its
feasibility for being manufactured. Moreover, the
transducer unit has to meet all the additional
specifications which are characteristic to the con
struction made according to the prior art referred to
hereinabove, including good shielding against external noise fields.
It has now been found that the direct coupling between the membrane and the piezoelectric transducer can be achieved by incorporating the piezoelectric transducer into the membrane itself. To carry out this idea it has been necessary to break with the conventional design of membranes, i.e.
with membranes in form of thin, often metallic, plates.
According to the present invention there is provided an electric transducer unit for sensing mechanical vibrations or other pressure changes, comprising a membrane for sensing said pressure changes and a piezoelectric transducer mechanically coupled to said membrane and comprising a pair of electrodes, in which said membrane comprises a membrane body of an elastic plastics material and said piezoelectric transducer is located in said membrane body, at least one of said electrodes being lead out through said membrane body.
The use of the membrane body completely pro techs the crystal of the piezoelectric transducer against any external mechanical impact, but at the same time the electric properties remain unchanged due to the direct coupling between the membrane body and the crystal.
An additional advantage occurs due to the greater mechanical strength of the membrane body, because in prior constructions high external forces could destroy not only the crystal but the membrane plate as well. Because the membrane used in the present invention is thicker than usual and elastic it will better resist these forces.
In a preferred embodiment of the invention an electrial conductive coating is provided on the outer surface of the membrane body.
Another embodiment which facilitates the manufacturing of the membrane body is made of two parts, the piezoelectric transducer abutting the inner wall of the outer part. This embodiment, in which the membrane body is made of two parts, is especially advantageous if the outer part of the membrane body is built integrally with a casing surrounding the outside of the transducer, and the inner part is placed in the inside of the casing. One of the electrode terminals and the shielding coating can be omitted when the outer part of the membrane body is made of an electrically conductive plastics material.
The membrane body can be manufactured of epoxide resin or of polystyrene or of polypropylene or of other similar elastic plastics materials.
In the accompanying drawings:
Figure 1 is a vertical sectional view, not to scale, of a first embodiment of the transducer unit according to the invention;
Figure 2 is a sectional view similar to Figure 1 but showing a shielding coating on the outer surface thereof;
Figure 3 is a vertical sectional view of another embodiment according to the invention;
Figure 4 is a vertical sectional view of a further embodiment according to the invention;
Figure 5 is a vertical sectional view of an embodiment according to the invention comprising a trans ducer unit similar to that shown in Figure 2;
Figure 6 is a vertical sectional view of the embodiment of Figure 1 illustrated to scale.
Figure 1 shows the simplest embodiment of the transducer unit in a vertical sectional view. The transducer unit comprises two constructional parts, namely a membrane body 1 and a piezoelectric transducer 2 placed inside the membrane body 1.
The piezoelectric transducer 2 is a square or rectangular prism with output electrode such as terminals 3 and 4 connected respectively to the opposite surfaces of the transducer 2 by means, for example, of a soldered connection.
The membrane body 1 is preferably circular in shape and has a thickness greater than that of the piezoelectric transducer 2. A condition for proper operation is that the membrane body 1 should transmit the mechanical effects (principally the bending and shear stresses caused by membranelike oscillation) to the piezoelectric transducer 2 located in it. The membrane body 1 should therefore be made of an elastic plastics material. Actually locating the piezoelectric transducer 2 can be achieved in many ways. However, a most convenient way is to mould the membrane body 1 around the transducer, so that forces which could destroy the crystal appear during the casting and the subsequent solidification steps.
In the embodiment shown in Figure 1 the transducer unit according to the invention can be used instead of the membrane of any kind of conventional transducer.
The embodiment shown in Figure 2 differs from the one shown in Figure 1 in that on the upper surface of the membrane body 1 a coating of electrically conductive material is made for completely shielding the housing of the transducer (Figure 5) against external electric noise and disturbing fields.
The coating 5 can be made by any known plastic metallisation process or by the application of a conductive paint.
The membrane body 1 shown in Figure 3 consists of two separate component parts, namely an upper portion la, and a lower portion 1b made of different materials. The upper portion la is made of an electrically conductive flexible plastics material so that there is no need for the coating 5, and the upper electrode surface of the piezoelectric transducer 2 is coupled directly to the electrically conductive upper portion 1a of the membrane body 1, whereby the terminal 3 can be dispensed with. An output lead for the upper crystal surface is provided by a wire 6 connected to or moulded or pressed in the upper portion 1 a. The lower portion 1b of the membrane body 1 is made of a non-conductive elastic plastics material and it is connected by moulding to the upper portion 1a. The lower electrode surface of the crystal has an output terminal 4.
Figure 4 shows an improved embodiment compared to that shown in Figure 3 in which the electrically conductive upper portion 1a of the membrane body 1 is designed to form also the side wall 7 of the transducer housing. The bottom of the housing is closed by a cover plate 10 and a perse known amplifier 8 for the transducer can be placed in a shielded chamber 9 so formed. The transducer output is lead out by a low impedance wire 11 from the output of the amplifier 8. Inside the housing the terminal 4 can be coupled directly to the input of thg amplifier 8. The body of the housing with a shielded chamber 9 serves as the other lead out terminal 3.
Figure 5 shows an embodiment which is similar to, that shown in Figure 4, but here the side wall 7 of the housing is separated from the membrane body 1.
The housing does not contain any amplifier in this case. The transducer unit is designed as that shown in Figure 2. The shielding coating 5 of the membrane body 1 is connected electrically to the metallic side wall 7 of the housing.
In Figure 6 the embodiment of Figure 1 is shown to scale. The membrane body 1 preferably has a diameter about 25 mm and a thickness about 1.5 mm. The crystal of the piezoelectric transducer 2 has a diameter of 16 mm and a thickness of 0.4 mm. Of course, sizes substantially differing from these exemplary values can also be used.
The membrane body can be made, for example, of epoxide resin, of polystyrene, of polypropylene or of other easily processable plastics materials.
As far as operation is concerned it is of no importance whether the transducer unit according to the invention is located completely or only partly in the membrane body 1. In a rugged design for measuring greater pressure changes the lower electrode surface of the piezoelectric transducer 2 may extend out of the bottom of the membrane body 1.
The measurements carried out with the transducer unit of the invention have proved that this unit is equivalent to conventional transducers as regards its sensitivity and electrical transmission.
However, when stability, reliability and life are considered the transducer according to the invention is substantially more favourable than conventional ones because the sensitive crystal is protected against any kind of external mechanical impacts on the membrane body 1. If the transducer according to the invention is accidentally dropped or its membrane surface is mechanically damaged, this cannot cause the splitting or breaking of the crystal of the transducer.
Claims (7)
1. An electric transducer unit for sensing mechanical vibrations or other pressure changes, comprising a membrane for sensing said pressure changes, and a piezoelectric transducer mechanically coupled to said membrane and comprising a pair of electrodes, in which said membrane comprises a m & - brane body of an elastic plastics material and said piezoelectric transducer is located in said membrane body, at least one of said electrodes being lead out through said membrane body.
2. A unit as claimed in claim 1, further comprising an electrically conductive coating on the outer surface of said membrane body.
3. A unit as claimed in claim 1, wherein said membrane body is made of an inner and an outer part and said piezoelectric transducer hurts the inner wall of said outer part,
4. A unit as claimed in claim 3, wherein said outer part of said membrane body is built integrally with a casing surrounding the outside of said unit and defining an inner chamber and said inner part is located in said inner chamber.
5. A unit as claimed in claim 3, wherein said outer part of said membrane body is made of an electrically conductive material.
6. A unit as claimed in any preceding claim, wherein said membrane body is made of an epoxide resin, of polystyrene or of polypropylene.
7. An electric transducer unit substantially as herein described with reference to Figures 1 and 6, or any one of Figures 2 to 5, of the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19803020617 DE3020617A1 (en) | 1980-05-30 | 1980-05-30 | ELECTRIC CONVERTER UNIT FOR DETECTING MECHANICAL VIBRATIONS O.A. PRESSURE CHANGES |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2080613A true GB2080613A (en) | 1982-02-03 |
Family
ID=6103614
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8018036A Withdrawn GB2080613A (en) | 1980-05-30 | 1980-06-02 | Piezoelectric transducer |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE3020617A1 (en) |
| GB (1) | GB2080613A (en) |
| NL (1) | NL8003229A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3504011A1 (en) * | 1985-02-06 | 1986-08-07 | Siemens AG, 1000 Berlin und 8000 München | Making contact with oscillating components by means of conductive rubber |
| EP0400163A1 (en) * | 1989-05-30 | 1990-12-05 | J. Factory Co., Ltd. | Electric drum |
| EP0483955A1 (en) * | 1990-10-29 | 1992-05-06 | Trw Inc. | Encapsulated ceramic device and method for embedding in composite structure |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3201164C1 (en) * | 1982-01-15 | 1983-05-19 | Telemit-Electronic GmbH, 8000 München | Noise-compensated close-talking microphone |
| FR2530108B1 (en) * | 1982-07-12 | 1986-08-22 | Geophysique Cie Gle | NEW HYDROPHONE |
-
1980
- 1980-05-30 DE DE19803020617 patent/DE3020617A1/en not_active Withdrawn
- 1980-06-02 GB GB8018036A patent/GB2080613A/en not_active Withdrawn
- 1980-06-03 NL NL8003229A patent/NL8003229A/en not_active Application Discontinuation
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3504011A1 (en) * | 1985-02-06 | 1986-08-07 | Siemens AG, 1000 Berlin und 8000 München | Making contact with oscillating components by means of conductive rubber |
| EP0400163A1 (en) * | 1989-05-30 | 1990-12-05 | J. Factory Co., Ltd. | Electric drum |
| EP0483955A1 (en) * | 1990-10-29 | 1992-05-06 | Trw Inc. | Encapsulated ceramic device and method for embedding in composite structure |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3020617A1 (en) | 1981-12-10 |
| NL8003229A (en) | 1982-01-04 |
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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) |