AU2020102628A4 - A low frequency piezoelectric underwater transducer based on fold-back structure - Google Patents
A low frequency piezoelectric underwater transducer based on fold-back structure Download PDFInfo
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- 238000005452 bending Methods 0.000 claims abstract description 57
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- 239000000919 ceramic Substances 0.000 claims abstract description 32
- 238000007789 sealing Methods 0.000 claims abstract description 22
- 230000008901 benefit Effects 0.000 abstract description 9
- 238000013461 design Methods 0.000 abstract description 8
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- 239000003822 epoxy resin Substances 0.000 abstract description 6
- 239000000463 material Substances 0.000 abstract description 6
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- 229920000647 polyepoxide Polymers 0.000 abstract description 6
- 230000009466 transformation Effects 0.000 abstract description 6
- 229910000640 Fe alloy Inorganic materials 0.000 abstract description 4
- 239000011149 active material Substances 0.000 abstract description 4
- 238000004026 adhesive bonding Methods 0.000 abstract description 4
- QUSDAWOKRKHBIV-UHFFFAOYSA-N dysprosium iron terbium Chemical compound [Fe].[Tb].[Dy] QUSDAWOKRKHBIV-UHFFFAOYSA-N 0.000 abstract description 4
- 238000005516 engineering process Methods 0.000 abstract description 4
- 230000008569 process Effects 0.000 abstract description 4
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- 229910001369 Brass Inorganic materials 0.000 abstract description 2
- 229910000737 Duralumin Inorganic materials 0.000 abstract description 2
- 229910000861 Mg alloy Inorganic materials 0.000 abstract description 2
- 229910000831 Steel Inorganic materials 0.000 abstract description 2
- SNAAJJQQZSMGQD-UHFFFAOYSA-N aluminum magnesium Chemical compound [Mg].[Al] SNAAJJQQZSMGQD-UHFFFAOYSA-N 0.000 abstract description 2
- 238000004458 analytical method Methods 0.000 abstract description 2
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 239000010951 brass Substances 0.000 abstract description 2
- 239000002131 composite material Substances 0.000 abstract description 2
- 238000001514 detection method Methods 0.000 abstract description 2
- 238000011161 development Methods 0.000 abstract description 2
- 229910001385 heavy metal Inorganic materials 0.000 abstract description 2
- 230000006872 improvement Effects 0.000 abstract description 2
- 239000007788 liquid Substances 0.000 abstract description 2
- 239000000314 lubricant Substances 0.000 abstract description 2
- 238000012423 maintenance Methods 0.000 abstract description 2
- 229910052751 metal Inorganic materials 0.000 abstract description 2
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- 150000002739 metals Chemical class 0.000 abstract description 2
- 229910052761 rare earth metal Inorganic materials 0.000 abstract description 2
- 150000002910 rare earth metals Chemical class 0.000 abstract description 2
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- 238000011160 research Methods 0.000 abstract description 2
- 230000035945 sensitivity Effects 0.000 abstract description 2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 2
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
- H04R17/005—Piezoelectric transducers; Electrostrictive transducers using a piezoelectric polymer
-
- 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
- B06B1/0607—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 multiple elements
- B06B1/0611—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 multiple elements in a pile
-
- 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
- G10K11/004—Mounting transducers, e.g. provided with mechanical moving or orienting device
- G10K11/006—Transducer mounting in underwater equipment, e.g. sonobuoys
- G10K11/008—Arrays of transducers
-
- 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
- G10K11/18—Methods or devices for transmitting, conducting or directing sound
- G10K11/26—Sound-focusing or directing, e.g. scanning
- G10K11/32—Sound-focusing or directing, e.g. scanning characterised by the shape of the source
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/02—Casings; Cabinets ; Supports therefor; Mountings therein
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/42—Combinations of transducers with fluid-pressure or other non-electrical amplifying means
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/44—Special adaptations for subaqueous use, e.g. for hydrophone
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R31/00—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor
- H04R31/006—Interconnection of transducer parts
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Multimedia (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Transducers For Ultrasonic Waves (AREA)
Abstract
A low frequency piezoelectric underwater transducer based on fold
back structure
TECHNICAL FIELD
[01] The invention relates to an underwater transducer, in particular to a low
frequency piezoelectric underwater transducer based on fold-back stacks, which
belongs to the field of electroacoustic sensor. It is one type of electroacoustic devices,
which finishes the transformation between acoustic energy and electrical energy in
water to be used as low frequency projector and hydrophone.
BACKGROUND
[02] So far, the sound waves are the most effective information carrier for
underwater detection, and the underwater transducer is an indispensable key device.
With the further development of modem sonar technology and the continuous
improvement of application requirements, the underwater transducer with low
frequency and small size is urgently needed. The relevant research has become the
important developing trend. Currently, the most widely used low frequency transducers
include: giant magnetostrictive underwater transducer, flextensional transducer and its
improved versions, flexural transducer, free-flooded ring transducer and so on.
[03] The literature (Steohen C. Butler, A 2.5 kHz magnetostrictive Tonpilz sonar
transducer design, Smart Structures and Materials 2002: Active Materials: Behavior
and Mechanics, Vol. 4669, 2002, P510-521.) disclosed a low frequency longitudinal
underwater transducer based on the composite bar, whose active material is terbium
dysprosium-iron alloy rare earth giant magnetostrictive material. This kind of
transducer takes full advantage of the low sound velocity characteristics of functional
material terbium-dysprosium-iron alloy to significantly reduce its resonance frequency,
but the transducer is 15 kg of the weight.
[04] The literature (Kenneth D. Rolt, History of the flextensional electro
acoustic transducer, The Journal of the Acoustical Society of America, March 1990,
Vol. 87, No. 3, P1340-1349.) and U.S. Patent US 4922470 both introduced the
underwater transducer based on the certain theories. In order to obtain the low
frequency acoustic radiation, the reasonable mechanical structure was utilized to realize
2
the transformation between the extensional vibration modes of active element and the
other vibration modes, such as the flexural vibration of thin shell. This kind of
transducer can easily obtain low frequency with resonance lower than 3 kHz, however,
most of them have a heavy weight of more than 3 kg and a relatively large size.
[05] The U.S. patent US 4709361 disclosed a flexural disk underwater
transducer, which applied the flexural vibration mode to achieve low-frequency
resonance, while the transducer is greatly affected by the boundary support conditions,
so its application is greatly limited.
[06] The literature (Teng Duo, Chen Hang, Zhu Ning, Finite Element Analysis
of Free-flooded Segmented Ring Transducer, Torpedo Technology, December 2008,
Volume 16, Issue 6, P44-47.) introduced the theory of the free-flooded ring by utilizing
the Helmholtz resonance liquid cavity to achieve its low-frequency resonance. The free
flooded ring transducer has the low-frequency Helmholtz resonance of 2.3 kHz. On the
other hand, its weight exceeds 4 kg.
[07] In summary, the above-mentioned underwater transducers can easily
achieve low-frequency electroacoustic transformation at the frequency of 1-3 kHz,
but they have some common disadvantages in practical applications: (1). Heavy mass
(generally several kilograms or even more than ten kilograms); (2). Large size; (3).
Limited application (especially, they are unsuitable for array arrangement); (4). High
cost. Therefore, strictly speaking, the above-mentioned transducers all have the
characteristics of low frequency, while they do not have the absolute advantages in
weight and size.
SUMMARY
[08] In order to solve the technical problem of the coexistence of low frequency
as well as light weight and small size of the underwater transducer, the proposed
invention provides a low frequency piezoelectric underwater transducer based on fold
back structure. Such a folding underwater transducer makes full use of the space of
transducer and the compact structure design, and reasonably combines the longitudinal
vibration mode and the flexural vibration mode of different components, while
implementing the characteristics of low frequency as well as light weight and small
3
size. It has the advantages of wide application, high electro-acoustic efficiency, low
cost, convenient application as projector and hydrophone and reliable operation.
[09] In order to solve the above technical problems, the technical scheme of the
proposed invention provides a low-frequency underwater transducer including a
radiating head, a tail mass, two bending beams, two front piezoelectric stacks, two rear
piezoelectric stacks, a middle anti-phase piezoelectric stack and a housing. The whole
structure is symmetrical.
[010] The piezoelectric stack is formed by an even number of piezoelectric
ceramic pieces in series. The polarization directions of two adjacent piezoelectric
ceramic pieces are opposite. On the adhered surfaces of the piezoelectric ceramic piece,
the electrodes are led out by the electrode plates. The same polarized electrode plates
of the piezoelectric stacks are electrically connected in parallel, and two terminals are
led according to the "positive" and "negative" polarization directions. There are
insulating shims at both ends of the piezoelectric stacks, and the appropriate prestress
is applied by the prestressed bolt. It should be noted that in order to always ensure that
the front and rear piezoelectric stacks are in opposite phase with the middle anti-phase
piezoelectric stack, it is necessary to connect the "polarization +" and "polarization -"
terminals of the front and rear piezoelectric stacks with the "polarization -" and
"polarization +" terminals of the middle anti-phase piezoelectric stack. At the same
time, in order to ensure the feasibility of the structure, the number of piezoelectric
ceramic pieces in the middle anti-phase piezoelectric stack should be less than that of
the front and rear piezoelectric stacks; The bending beams together with the radiating
head and the tail mass should be respectively glued to the two ends of the piezoelectric
stacks, so that the piezoelectric stacks can be formed as a "Z" shaped fold-back structure
like a folding ruler.
[011] The front radiator with light metals such as duralumin or aluminum
magnesium alloy is made into a structure of truncated cone for increasing the radiation
area; The tail mass is of a cylindrical structure, with heavy metals such as steel and
brass; The purpose of this design is to obtain a larger vibration velocity ratio of the front
and rear surfaces, so as to increase the acoustic radiation of the front radiation surface.
4
[012] The proposed invention provides a low frequency piezoelectric underwater
transducer based on fold-back structure, which solves the technical problem of the
coexistence of low frequency as well as light weight and small size by reasonably
utilizing the longitudinal vibration mode of the piezoelectric stacks and the flexural
vibration mode of the bending beams. Such a folding underwater transducer has the
following beneficial effects: the fold-back structure makes full use of the space of
transducer, effectively increases the sound power capacity and improves the
transmitting ability and receiving sensitivity of the underwater transducer; The low
frequency piezoelectric underwater transducer based on fold-back structure also has the
advantages of simple structure, convenient manufacture, low cost, convenient assembly
and dis-assembly, and wide application. In particular, the way of transmitting the
acoustic energy form the front radiating surface will facilitate the application of the
transducer, making it more widely used and more suitable for array arrangement.
BRIEF DESCRIPTION OF THE FIGURES
[013] Hereinafter, a low frequency piezoelectric underwater transducer based on
fold-back structure of the proposed invention will be described in further detail with
reference to the attached drawings and examples.
[014] Fig. 1 is a schematic diagram of the structure of the low frequency
piezoelectric underwater transducer based on fold-back structure of the proposed
invention.
[015] Fig. 2 is a schematic diagram of the structure and the cascade relationship
of the middle anti-phase piezoelectric stack of the folding transducer of the proposed
invention.
[016] Fig. 3 is a schematic diagram of the structure and the cascade relationship
of the front piezoelectric stacks of the folding transducer of the proposed invention.
[017] Fig. 4 is a schematic diagram of the structure and cascade relationship of
the rear piezoelectric stacks of the folding transducer of the proposed invention.
[018] Component in the figures:
5
[019] 1. Radiating head; 2. Sealing ring; 3. Front bending beam; 4. Front
piezoelectric stack; 5. Middle anti-phase piezoelectric stack; 6. Rear piezoelectric stack;
7. Housing; 8. Rear bending beam; 9. Tail mass; 10. Positioning bolt; 11. Positioning
hole of the housing; 12. Positioning screw hole; 13. Output cable; 14. Insulating shim;
15. Electrode plate; 16. Electrode connecting wire; 17. Piezoelectric ceramic plate; 18.
Insulating sleeve; 19. Spring shim; 20. Prestressed bolt.
DESCRIPTION OF THE INVENTION
[020] This example demonstrates a low frequency piezoelectric underwater
transducer based on fold-back structure including a radiating head (1), a tail mass (9),
a front bending beam (3), front piezoelectric stacks (4), a middle anti-phase
piezoelectric stack (5), rear piezoelectric stacks (6), a rear bending beam(8), a housing
(7) and an output cable (13).
[021] As shown in Figure 1, the radiating head (1) of the proposed invention is of
the truncated cone structure with a sealing ring (2); The tail mass (9) is cylindrical with
a sealing ring (2); The housing (7) is cylindrical, which is combined with two sealing
rings (2) to complete underwater sealing; The positioning hole (11) of the housing is
provided on the housing (7), and the positioning screw hole (12) is provided on the tail
mass (9); The positioning bolt (10) is for the positioning of the housing (7); The output
cable (13) connects the electrodes of the piezoelectric stacks to the external driving
source, passing through the tail mass (9); There are three types of piezoelectric stacks,
namely front piezoelectric stacks (4), rear piezoelectric stacks (6) and middle anti-phase
piezoelectric stack (5), which combine with the front bending beam (3) and the rear
bending beam (8) to realize a "Z" shaped fold-back structure like a folding ruler. The
total number of the front piezoelectric stacks (4) which are glued parallelly between the
radiating head (1) and the rear bending beam (8) is two; The total number of the rear
piezoelectric stacks (6) which are glued parallelly between the tail mass (9) and the
front bending beam (3) is two; There is only one middle anti-phase piezoelectric stack
(5) glued between the front bending beam (3) and the rear bending beam (8).
Meanwhile, the front bending beam (3) and the rear bending beam (8) are perpendicular
to each other is necessary.
6
[022] The above-mentioned three types of piezoelectric stacks all need to be
properly prestressed by the prestressed bolt (20). The prestressed bolt (20) is inserted
in insulating sleeves (18) and combined with the spring shim (19). All piezoelectric
stacks are formed by glueing an even number of piezoelectric ceramic pieces (17) in
series. There is an insulating shim (14) at each end of the piezoelectric stacks. The
polarization directions of the two adjacent piezoelectric ceramic pieces are opposite.
Moreover, the electrodes are led out by electrode plates (15) on the adhered surface,
and the identical electrode of each piezoelectric stack are electrically connected in
parallel by electrode connecting wires (16).
[023] There are two points need to be noted. One is that in order to always ensure
that the front piezoelectric stacks (4) and rear piezoelectric stacks (6) are in opposite
phase with the middle anti-phase piezoelectric stack (5), it is necessary to connect the
"polarization +" and "polarization -" terminals of the front and rear piezoelectric stacks
with the "polarization -" and "polarization +" terminals of the middle anti-phase
piezoelectric stack (5), and they are connected to the same external driving source. The
other is that the number of piezoelectric ceramic pieces of the middle anti-phase
piezoelectric stack should be less than that of the front and rear piezoelectric stacks for
the feasibility of the structure.
[024] The specific assembly processes of the low frequency piezoelectric
underwater transducer based on fold-back structure are as follows:
[025] 1. Firstly, the piezoelectric ceramic plate (17) and the electrode plate (15)
are glued together in cross series with epoxy resin, and then the insulating shim (14) is
glued at both ends to form the middle anti-phase piezoelectric stack (5). The
polarization direction of the piezoelectric ceramic plate is shown in Fig. 2;
[026] 2. The middle anti-phase piezoelectric stack (5) is glued with the front
bending beam (3) and the rear bending beam (8), which appropriate prestress is applied
to by the prestressed bolt (20). The prestressed bolt (20) covered with insulating sleeves
(18) needs to match with the spring shim (19). During the glueing process, it is
necessary to ensure that the front bending beam (3) and the rear bending beam (8) are
perpendicular to each other, which is as shown in Fig. 2;
7
[027] 3. The piezoelectric ceramic plate (17) and the electrode plate (15) are glued
together in cross series with epoxy resin, and the insulating shim (14) is glued at both
ends to form the front piezoelectric stacks (4). The polarization direction of
piezoelectric ceramic plate is shown in Fig. 3;
[028] 4. Two groups of the front piezoelectric stacks (4) are glued parallelly
between the radiating head (1) and the rear bending beam (8), which appropriate
prestress is applied to by the prestressed bolt (20). The stress rod (20) covered with
insulating sleeves (18) needs to match with the spring shim (19). The above is as shown
in Fig. 3;
[029] 5. The piezoelectric ceramic plate (17) and the electrode plate (15) are glued
together in cross series with epoxy resin, and the insulating shim (14) is glued at both
ends to form the rear piezoelectric stacks (6) for two groups. The polarization direction
of piezoelectric ceramic plate is shown in Fig. 4;
[030] 6. Two groups of the rear piezoelectric stacks (6) are glued parallelly
between the front bending beam (3) and the tail mass (9), which appropriate prestress
is applied by the prestressed bolt (20). The prestressed bolt (20) inserted in insulating
sleeves (18) needs to match with the spring shim (19). The above is as shown in Fig. 4;
[031] 7. The electrodes (15) of the above-mentioned piezoelectric stacks are
connected in parallel, and the next step is to connect the "polarization +" and
"polarization -" terminals of the front and rear piezoelectric stacks with the "polarization
-" and "polarization +" terminals of the middle anti-phase piezoelectric stacks (5),
which is as shown in Fig. 2, Fig. 3 and Fig. 4;
[032] 8. The output cable (13) connects the electrodes of the above piezoelectric
stacks, passing through the tail mass (9);
[033] 9. The sealing rings (2) are evenly coated with lubricant and placed in the
corresponding sealing grooves of the radiating head (1) and the tail mass (9);
8
[034] 10. The housing (7) is sleeved from the back end to complete the underwater
sealing of the transducer, which is positioned by one positioning bolt (10).
[035] The main functions realized by the low frequency piezoelectric underwater
transducer based on fold-back structure of the proposed invention are as follows:
[036] The transducer has a better performance in both transmitting and receiving
of underwater acoustic waves; the fold-back structure of transducer will significantly
increase the acoustic power capacity, make full use of the space of transducer and
reasonably combine the longitudinal vibration mode and the flexural vibration mode of
different components, while implementing the characteristics of low frequency as well
as light weight and small size; The way of transmitting acoustic energy by utilizing the
piston transmitting head makes the application of the transducer more extensive
applied, especially suitable for array arrangement; The waterproof design of the housing
combined with the sealing rings makes the transducer more convenient in daily
maintenance and repair.
[037] Although the invention has been described with reference to specific
examples, it will be appreciated by those skilled in the art that the invention may be
embodied in many other forms, in keeping with the broad principles and the spirit of
the invention described herein.
[038] The present invention and the described embodiments specifically include
the best method known to the applicant of performing the invention. The present
invention and the described preferred embodiments specifically include at least one
feature that is industrially applicable
Description
A low frequency piezoelectric underwater transducer based on fold back structure
[01] The invention relates to an underwater transducer, in particular to a low frequency piezoelectric underwater transducer based on fold-back stacks, which belongs to the field of electroacoustic sensor. It is one type of electroacoustic devices, which finishes the transformation between acoustic energy and electrical energy in water to be used as low frequency projector and hydrophone.
[02] So far, the sound waves are the most effective information carrier for underwater detection, and the underwater transducer is an indispensable key device. With the further development of modem sonar technology and the continuous improvement of application requirements, the underwater transducer with low frequency and small size is urgently needed. The relevant research has become the important developing trend. Currently, the most widely used low frequency transducers include: giant magnetostrictive underwater transducer, flextensional transducer and its improved versions, flexural transducer, free-flooded ring transducer and so on.
[03] The literature (Steohen C. Butler, A 2.5 kHz magnetostrictive Tonpilz sonar transducer design, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics, Vol. 4669, 2002, P510-521.) disclosed a low frequency longitudinal underwater transducer based on the composite bar, whose active material is terbium dysprosium-iron alloy rare earth giant magnetostrictive material. This kind of transducer takes full advantage of the low sound velocity characteristics of functional material terbium-dysprosium-iron alloy to significantly reduce its resonance frequency, but the transducer is 15 kg of the weight.
[04] The literature (Kenneth D. Rolt, History of the flextensional electro acoustic transducer, The Journal of the Acoustical Society of America, March 1990, Vol. 87, No. 3, P1340-1349.) and U.S. Patent US 4922470 both introduced the underwater transducer based on the certain theories. In order to obtain the low frequency acoustic radiation, the reasonable mechanical structure was utilized to realize the transformation between the extensional vibration modes of active element and the other vibration modes, such as the flexural vibration of thin shell. This kind of transducer can easily obtain low frequency with resonance lower than 3 kHz, however, most of them have a heavy weight of more than 3 kg and a relatively large size.
[05] The U.S. patent US 4709361 disclosed a flexural disk underwater transducer, which applied the flexural vibration mode to achieve low-frequency resonance, while the transducer is greatly affected by the boundary support conditions, so its application is greatly limited.
[06] The literature (Teng Duo, Chen Hang, Zhu Ning, Finite Element Analysis of Free-flooded Segmented Ring Transducer, Torpedo Technology, December 2008, Volume 16, Issue 6, P44-47.) introduced the theory of the free-flooded ring by utilizing the Helmholtz resonance liquid cavity to achieve its low-frequency resonance. The free flooded ring transducer has the low-frequency Helmholtz resonance of 2.3 kHz. On the other hand, its weight exceeds 4 kg.
[07] In summary, the above-mentioned underwater transducers can easily achieve low-frequency electroacoustic transformation at the frequency of 1-3 kHz,
but they have some common disadvantages in practical applications: (1). Heavy mass (generally several kilograms or even more than ten kilograms); (2). Large size; (3). Limited application (especially, they are unsuitable for array arrangement); (4). High cost. Therefore, strictly speaking, the above-mentioned transducers all have the characteristics of low frequency, while they do not have the absolute advantages in weight and size.
[08] In order to solve the technical problem of the coexistence of low frequency as well as light weight and small size of the underwater transducer, the proposed invention provides a low frequency piezoelectric underwater transducer based on fold back structure. Such a folding underwater transducer makes full use of the space of transducer and the compact structure design, and reasonably combines the longitudinal vibration mode and the flexural vibration mode of different components, while implementing the characteristics of low frequency as well as light weight and small size. It has the advantages of wide application, high electro-acoustic efficiency, low cost, convenient application as projector and hydrophone and reliable operation.
[09] In order to solve the above technical problems, the technical scheme of the proposed invention provides a low-frequency underwater transducer including a radiating head, a tail mass, two bending beams, two front piezoelectric stacks, two rear piezoelectric stacks, a middle anti-phase piezoelectric stack and a housing. The whole structure is symmetrical.
[010] The piezoelectric stack is formed by an even number of piezoelectric ceramic pieces in series. The polarization directions of two adjacent piezoelectric ceramic pieces are opposite. On the adhered surfaces of the piezoelectric ceramic piece, the electrodes are led out by the electrode plates. The same polarized electrode plates of the piezoelectric stacks are electrically connected in parallel, and two terminals are led according to the "positive" and "negative" polarization directions. There are insulating shims at both ends of the piezoelectric stacks, and the appropriate prestress is applied by the prestressed bolt. It should be noted that in order to always ensure that the front and rear piezoelectric stacks are in opposite phase with the middle anti-phase piezoelectric stack, it is necessary to connect the "polarization +" and "polarization -" terminals of the front and rear piezoelectric stacks with the "polarization -" and "polarization +" terminals of the middle anti-phase piezoelectric stack. At the same time, in order to ensure the feasibility of the structure, the number of piezoelectric ceramic pieces in the middle anti-phase piezoelectric stack should be less than that of the front and rear piezoelectric stacks; The bending beams together with the radiating head and the tail mass should be respectively glued to the two ends of the piezoelectric stacks, so that the piezoelectric stacks can be formed as a "Z" shaped fold-back structure like a folding ruler.
[011] The front radiator with light metals such as duralumin or aluminum magnesium alloy is made into a structure of truncated cone for increasing the radiation area; The tail mass is of a cylindrical structure, with heavy metals such as steel and brass; The purpose of this design is to obtain a larger vibration velocity ratio of the front and rear surfaces, so as to increase the acoustic radiation of the front radiation surface.
[012] The proposed invention provides a low frequency piezoelectric underwater transducer based on fold-back structure, which solves the technical problem of the coexistence of low frequency as well as light weight and small size by reasonably utilizing the longitudinal vibration mode of the piezoelectric stacks and the flexural vibration mode of the bending beams. Such a folding underwater transducer has the following beneficial effects: the fold-back structure makes full use of the space of transducer, effectively increases the sound power capacity and improves the transmitting ability and receiving sensitivity of the underwater transducer; The low frequency piezoelectric underwater transducer based on fold-back structure also has the advantages of simple structure, convenient manufacture, low cost, convenient assembly and dis-assembly, and wide application. In particular, the way of transmitting the acoustic energy form the front radiating surface will facilitate the application of the transducer, making it more widely used and more suitable for array arrangement.
[013] Hereinafter, a low frequency piezoelectric underwater transducer based on fold-back structure of the proposed invention will be described in further detail with reference to the attached drawings and examples.
[014] Fig. 1 is a schematic diagram of the structure of the low frequency
piezoelectric underwater transducer based on fold-back structure of the proposed invention.
[015] Fig. 2 is a schematic diagram of the structure and the cascade relationship of the middle anti-phase piezoelectric stack of the folding transducer of the proposed invention.
[016] Fig. 3 is a schematic diagram of the structure and the cascade relationship of the front piezoelectric stacks of the folding transducer of the proposed invention.
[017] Fig. 4 is a schematic diagram of the structure and cascade relationship of the rear piezoelectric stacks of the folding transducer of the proposed invention.
[018] Component in the figures:
[019] 1. Radiating head; 2. Sealing ring; 3. Front bending beam; 4. Front piezoelectric stack; 5. Middle anti-phase piezoelectric stack; 6. Rear piezoelectric stack; 7. Housing; 8. Rear bending beam; 9. Tail mass; 10. Positioning bolt; 11. Positioning hole of the housing; 12. Positioning screw hole; 13. Output cable; 14. Insulating shim; 15. Electrode plate; 16. Electrode connecting wire; 17. Piezoelectric ceramic plate; 18. Insulating sleeve; 19. Spring shim; 20. Prestressed bolt.
[020] This example demonstrates a low frequency piezoelectric underwater transducer based on fold-back structure including a radiating head (1), a tail mass (9), a front bending beam (3), front piezoelectric stacks (4), a middle anti-phase piezoelectric stack (5), rear piezoelectric stacks (6), a rear bending beam(8), a housing (7) and an output cable (13).
[021] As shown in Figure 1, the radiating head (1) of the proposed invention is of the truncated cone structure with a sealing ring (2); The tail mass (9) is cylindrical with a sealing ring (2); The housing (7) is cylindrical, which is combined with two sealing rings (2) to complete underwater sealing; The positioning hole (11) of the housing is provided on the housing (7), and the positioning screw hole (12) is provided on the tail mass (9); The positioning bolt (10) is for the positioning of the housing (7); The output cable (13) connects the electrodes of the piezoelectric stacks to the external driving source, passing through the tail mass (9); There are three types of piezoelectric stacks, namely front piezoelectric stacks (4), rear piezoelectric stacks (6) and middle anti-phase piezoelectric stack (5), which combine with the front bending beam (3) and the rear bending beam (8) to realize a "Z" shaped fold-back structure like a folding ruler. The total number of the front piezoelectric stacks (4) which are glued parallelly between the radiating head (1) and the rear bending beam (8) is two; The total number of the rear piezoelectric stacks (6) which are glued parallelly between the tail mass (9) and the front bending beam (3) is two; There is only one middle anti-phase piezoelectric stack (5) glued between the front bending beam (3) and the rear bending beam (8). Meanwhile, the front bending beam (3) and the rear bending beam (8) are perpendicular to each other is necessary.
[022] The above-mentioned three types of piezoelectric stacks all need to be properly prestressed by the prestressed bolt (20). The prestressed bolt (20) is inserted in insulating sleeves (18) and combined with the spring shim (19). All piezoelectric stacks are formed by glueing an even number of piezoelectric ceramic pieces (17) in series. There is an insulating shim (14) at each end of the piezoelectric stacks. The polarization directions of the two adjacent piezoelectric ceramic pieces are opposite. Moreover, the electrodes are led out by electrode plates (15) on the adhered surface, and the identical electrode of each piezoelectric stack are electrically connected in parallel by electrode connecting wires (16).
[023] There are two points need to be noted. One is that in order to always ensure that the front piezoelectric stacks (4) and rear piezoelectric stacks (6) are in opposite phase with the middle anti-phase piezoelectric stack (5), it is necessary to connect the "polarization +" and "polarization -" terminals of the front and rear piezoelectric stacks with the "polarization -" and "polarization +" terminals of the middle anti-phase piezoelectric stack (5), and they are connected to the same external driving source. The other is that the number of piezoelectric ceramic pieces of the middle anti-phase piezoelectric stack should be less than that of the front and rear piezoelectric stacks for the feasibility of the structure.
[024] The specific assembly processes of the low frequency piezoelectric underwater transducer based on fold-back structure are as follows:
[025] 1. Firstly, the piezoelectric ceramic plate (17) and the electrode plate (15) are glued together in cross series with epoxy resin, and then the insulating shim (14) is glued at both ends to form the middle anti-phase piezoelectric stack (5). The polarization direction of the piezoelectric ceramic plate is shown in Fig. 2;
[026] 2. The middle anti-phase piezoelectric stack (5) is glued with the front bending beam (3) and the rear bending beam (8), which appropriate prestress is applied to by the prestressed bolt (20). The prestressed bolt (20) covered with insulating sleeves (18) needs to match with the spring shim (19). During the glueing process, it is necessary to ensure that the front bending beam (3) and the rear bending beam (8) are perpendicular to each other, which is as shown in Fig. 2;
[027] 3. The piezoelectric ceramic plate (17) and the electrode plate (15) are glued together in cross series with epoxy resin, and the insulating shim (14) is glued at both ends to form the front piezoelectric stacks (4). The polarization direction of piezoelectric ceramic plate is shown in Fig. 3;
[028] 4. Two groups of the front piezoelectric stacks (4) are glued parallelly between the radiating head (1) and the rear bending beam (8), which appropriate prestress is applied to by the prestressed bolt (20). The stress rod (20) covered with insulating sleeves (18) needs to match with the spring shim (19). The above is as shown in Fig. 3;
[029] 5. The piezoelectric ceramic plate (17) and the electrode plate (15) are glued together in cross series with epoxy resin, and the insulating shim (14) is glued at both ends to form the rear piezoelectric stacks (6) for two groups. The polarization direction of piezoelectric ceramic plate is shown in Fig. 4;
[030] 6. Two groups of the rear piezoelectric stacks (6) are glued parallelly between the front bending beam (3) and the tail mass (9), which appropriate prestress is applied by the prestressed bolt (20). The prestressed bolt (20) inserted in insulating sleeves (18) needs to match with the spring shim (19). The above is as shown in Fig. 4;
[031] 7. The electrodes (15) of the above-mentioned piezoelectric stacks are connected in parallel, and the next step is to connect the "polarization +" and "polarization -" terminals of the front and rear piezoelectric stacks with the "polarization -" and "polarization +" terminals of the middle anti-phase piezoelectric stacks (5), which is as shown in Fig. 2, Fig. 3 and Fig. 4;
[032] 8. The output cable (13) connects the electrodes of the above piezoelectric stacks, passing through the tail mass (9);
[033] 9. The sealing rings (2) are evenly coated with lubricant and placed in the corresponding sealing grooves of the radiating head (1) and the tail mass (9);
[034] 10. The housing (7) is sleeved from the back end to complete the underwater sealing of the transducer, which is positioned by one positioning bolt (10).
[035] The main functions realized by the low frequency piezoelectric underwater transducer based on fold-back structure of the proposed invention are as follows:
[036] The transducer has a better performance in both transmitting and receiving of underwater acoustic waves; the fold-back structure of transducer will significantly increase the acoustic power capacity, make full use of the space of transducer and reasonably combine the longitudinal vibration mode and the flexural vibration mode of different components, while implementing the characteristics of low frequency as well as light weight and small size; The way of transmitting acoustic energy by utilizing the piston transmitting head makes the application of the transducer more extensive applied, especially suitable for array arrangement; The waterproof design of the housing combined with the sealing rings makes the transducer more convenient in daily maintenance and repair.
[037] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms, in keeping with the broad principles and the spirit of the invention described herein.
[038] The present invention and the described embodiments specifically include the best method known to the applicant of performing the invention. The present invention and the described preferred embodiments specifically include at least one feature that is industrially applicable
The invention discloses a low frequency piezoelectric underwater transducer based on fold-back structure, which includes a radiating head, a tail mass, a front bending beam, front piezoelectric stacks, a middle anti-phase piezoelectric stack, rear piezoelectric stacks, a rear bending beam, a housing and an output cable. The front and rear bending beams, together with the radiating head and the tail mass, are respectively glued to the two ends of the piezoelectric stacks in a certain arrangement, so that the piezoelectric stacks can be formed as a "Z" shaped fold-back structure like a folding ruler. The housing is combined with the sealing rings to realize underwater sealing. The output cable connects the electrodes of the piezoelectric stacks to the external driving source, passing through the tail mass. The invention makes full use of the space of the transducer, and it significantly increases its sound power capacity. By the suitable combination of the longitudinal vibration mode of the piezoelectric stacks and the flexural vibration mode of the bending beams, an underwater transducer with low frequency as well as a small size will be proposed. Moreover, the transducer also has the advantages of simple structure, convenient manufacture, low cost, convenient assembly and dis-assembly, and wide application.
Claims (9)
1. The low frequency piezoelectric underwater transducer based on fold-back structure, which includes a radiating head (1), a tail mass (9), a front bending beam (3), front piezoelectric stacks (4), a middle anti-phase piezoelectric stack (5), rear piezoelectric stacks (6), a rear bending beam(8), a housing (7) and an output cable (13). The front and rear bending beams, together with the radiating head (1) and the tail mass (9), are respectively glued to the two ends of the piezoelectric stacks in a certain arrangement. The housing (7) is combined with the sealing rings (2) to realize underwater sealing. The output cable (13) connects the electrodes of the piezoelectric stacks to the external driving source, passing through the tail mass (9).
2. The low frequency piezoelectric underwater transducer based on fold-back structure according to claim 1 is characterized in that: the front piezoelectric stacks (4), the rear piezoelectric stacks (6) and the middle anti-phase piezoelectric stack (5) together combine with the front bending beam (3) and the rear bending beam (8), so as to realize a "Z" shaped fold-back structure like a folding ruler.
3. The low frequency piezoelectric underwater transducer based on fold-back structure according to claim 1 is characterized in that: the piezoelectric stacks are composed of an even number of piezoelectric ceramic pieces (17) in series, and the identical electrode of each piezoelectric stack are electrically connected in parallel by an electrode connecting wire (16).
4. The low frequency piezoelectric underwater transducer based on fold-back structure according to claim 1 is characterized in that: according to the polarization direction of the piezoelectric ceramic pieces (17), the "polarization +" and "polarization -" terminals of the front and rear piezoelectric stacks are connected with the "polarization -" and "polarization +" terminals of the middle anti-phase piezoelectric stack (5).
5. The low frequency piezoelectric underwater transducer based on fold-back structure according to claim 1 or claim 2 is characterized in that: the number of piezoelectric ceramic pieces of the middle anti-phase piezoelectric stacks (5) should be less than that of the front and rear piezoelectric stack.
6. The low frequency underwater transducer of fold-back piezoelectric ceramics according to claim 1 or claim 2 is characterized in that: there is only one middle anti phase piezoelectric stack (5) glued between the front bending beam (3) and the rear bending beam (8). Meanwhile, that the front bending beam (3) and the rear bending beam (8) are perpendicular to each other is necessary.
7. The low frequency piezoelectric underwater transducer based on fold-back structure according to claim 1 and claim 2 is characterized in that: there are two front piezoelectric stacks (4), which are glued parallelly between the radiating head (1) and the rear bending beam (8).
8. The low frequency piezoelectric underwater transducer based on fold-back structure according to claim 1 and claim 2 is characterized in that: there are two rear piezoelectric stacks (6), which are glued in parallel between the tail mass (9) and the front bending beam (3).
9. The low frequency piezoelectric underwater transducer based on fold-back structure according to claim 1 is characterized in that: all of the above piezoelectric stacks need to be prestressed appropriately by prestressed bolts (20).
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