Ultrasonic transducer structure

Abstract

The invention discloses an ultrasonic transducer structure which comprises a transducer shell, a piezoelectric vibrator, an acoustic matching layer and a sound absorption backing. The piezoelectric vibrator comprises a first piezoelectric material layer and a second piezoelectric material layer. The piezoelectric vibrator has the beneficial effects that the first piezoelectric material layer and the second piezoelectric material layer are arranged, the first piezoelectric material layer and the second piezoelectric material layer are electrically parallel piezoelectric material layers with opposite polarization directions, and the ground capacitance of the piezoelectric vibrator is multiplied by stacking two crystals with opposite polarization directions; and meanwhile, the frequency generated by the total thickness of the stacked piezoelectric crystal is equal to the frequency generated by a single piezoelectric crystal, so that the contradiction between the frequency of a traditional piezoelectric vibrator and the capacitance is solved.

Description

Technical Field

[0001] The invention relates to a transducer, in particular to an ultrasonic transducer structure, belonging to the technical field of transducers. Background Art

[0002] Medium and low frequency ultrasonic transducers include acoustic transducers such as diagnostic ultrasound, sonar, and non-destructive testing, and their application frequency is usually 1MHz or below. Since the application frequency of traditional acoustic transducers is inversely proportional to the thickness of the piezoelectric vibrator, the piezoelectric vibrator of medium and low frequency ultrasonic transducers is usually thicker. At the same time, since the capacitance of the transducer array element is inversely proportional to the thickness of the vibrator, the capacitance of the vibrator of the medium and low frequency ultrasonic transducer is usually small due to the excessive thickness, which causes the problem of mismatch with the electrical impedance of the back-end system. The above contradiction needs to be resolved. The usual practice is to increase the capacitance by increasing the relative dielectric constant of the piezoelectric vibrator, such as using PMN-PT crystals to replace PZT ceramics. On the one hand, the high capacitance of the crystal makes the electrical impedance matching better, and on the other hand, the ultra-high electromechanical coupling coefficient of the PMN-PT crystal makes other indicators of the transducer higher. However, the capacitance improvement efficiency of this solution is limited. Especially in the current situation where 2D transducers are widely used, the vibrator size of ultrasonic transducers is getting smaller and smaller. It is urgent to find a method that can efficiently increase the capacitance without affecting the performance of other transducers.

[0003] In the prior art, as disclosed in the ultrasonic transducer, ultrasonic probe and ultrasonic transducer manufacturing method of announcement number CN116528653A, the ultrasonic transducer includes: a matching backing body, which is an integrated structure; a piezoelectric body, which is arranged inside the matching backing body, and the matching backing body wraps all the outer walls of the piezoelectric body. In the present invention, the outer wall of the piezoelectric body wraps the matching backing body, and no adhesive layer is required when the piezoelectric body is fixed, and each side wall is directly in contact with the matching backing body. The ultrasonic transducer of this structure reduces the length of the heat conduction material path between the piezoelectric body and the matching backing body, and at the same time increases the contact area between the piezoelectric body and the matching backing body, which can effectively ensure that the heat conduction path of the outer wall of the piezoelectric body is not interrupted, further reducing the thermal resistance of the overall structure, not only reducing the number of components required for the ultrasonic transducer, but also improving the overall heat dissipation effect, effectively solving the problem of poor heat dissipation effect of the heat dissipation structure of the existing ultrasonic transducer, but for the existing medium and low frequency ultrasonic transducers, there is mainly a problem of insufficient sensitivity due to impedance mismatch, because the capacitance of PZT ceramics is low, which is due to the limitation of component size and thickness. After replacing the PMN-PT crystal, the capacitance increased by about 20-40%, but this improvement is still limited and cannot justify the high cost of the PMN-PT crystal. Secondly, the low coercive field leads to insufficient signal strength. Although PMN-PT crystal can improve the bandwidth of the transducer, it cannot match the hard PZT ceramic in terms of transducer signal strength due to the low driving voltage caused by the low coercive field. The development of ternary PIN-PMN-PT crystal and Mn-doped PIN-PMN-PT crystal has enhanced the coercive field of PMN-PT from about 2.5kV / cm to 5kV / cm, which is not a small number, but it is still lower than the approximately 10kV / cm that can be easily obtained from PZT ceramics. Summary of the invention

[0004] The object of the present invention is to provide an ultrasonic transducer structure in order to solve at least one of the above technical problems.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions: an ultrasonic transducer structure, including a transducer housing, a piezoelectric vibrator, an acoustic matching layer, and a sound absorbing backing, wherein the piezoelectric vibrator, the acoustic matching layer, and the sound absorbing backing are all arranged in the transducer housing, and the acoustic matching layer, the piezoelectric vibrator, and the sound absorbing backing are stacked together in sequence from top to bottom;

[0006] The piezoelectric vibrator transmits and receives signals through the piezoelectric effect between mechanical energy and electrical energy. The piezoelectric vibrator includes a first piezoelectric material layer and a second piezoelectric material layer, and the first piezoelectric material layer and the second piezoelectric material layer are stacked up and down.

[0007] The acoustic matching layer is between the piezoelectric vibrator and the object to be measured. A bottom circuit board is also arranged in the transducer housing. The sound-absorbing backing is between the piezoelectric vibrator and the bottom circuit board.

[0008] As a further solution of the present invention: the first piezoelectric material layer and the second piezoelectric material layer constituting the piezoelectric vibrator include but are not limited to lead zirconate titanate ceramics, lead magnesium niobate-lead titanate crystals, lead indium niobate-lead magnesium niobate-lead titanate crystals, lead zinc niobate-lead titanate crystals, or crystals doped with manganese, iron, cobalt, and samarium elements, and may also be 1-3 or 2-2 type composite materials composed of the above crystals or ceramics and polymer compounds.

[0009] As a further solution of the present invention: the acoustic matching layer is provided with one or more layers, and the acoustic matching layer is composed of a high molecular polymer or a high molecular polymer metal or ceramic composite material.

[0010] As a further solution of the present invention: the sound absorbing backing is composed of a graphite composite material, a high molecular polymer containing tungsten powder, or a metal composite material.

[0011] As a further solution of the present invention: the bottom circuit board is connected with an electrical lead, and the other end of the electrical lead is connected with a host computer / system of the peripheral device for signal transmission.

[0012] As a further solution of the present invention: the electrical leads are formed by metal wires, PCB circuit boards or ASIC integrated circuits.

[0013] As a further solution of the present invention: the first piezoelectric material layer and the second piezoelectric material layer are electrically parallel piezoelectric material layers with opposite polarization directions.

[0014] The beneficial effects of the present invention are as follows: the present invention is provided with a first piezoelectric material layer and a second piezoelectric material layer, and the first piezoelectric material layer and the second piezoelectric material layer are electrically parallel piezoelectric material layers with opposite polarization directions. By stacking two crystals with opposite polarization directions, the capacitance of the piezoelectric vibrator is multiplied, thereby better matching the electrical impedance between the transducer and the system. At the same time, the frequency generated by the total thickness of the stacked piezoelectric crystals is equivalent to the frequency generated by a single piezoelectric crystal, thereby solving the contradiction between the frequency and capacitance of the traditional piezoelectric vibrator. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the appearance structure of the transducer of the present invention;

[0016] Figure 2 It is a schematic diagram of the cross-sectional structure of the transducer of the present invention;

[0017] Figure 3 It is a schematic diagram of the structure of a single-element stacked transducer of the present invention;

[0018] Figure 4 It is a schematic diagram of the structure of a conventional single-element transducer of the present invention;

[0019] Figure 5 It is a schematic diagram for comparing the performance of the transducer of the present invention;

[0020] Figure 6 It is a schematic diagram of the comparative structure of the transducer response amplitude of the present invention.

[0021] In the figure: 1. transducer housing, 2. piezoelectric vibrator, 21. first piezoelectric material layer, 22. second piezoelectric material layer, 3. acoustic matching layer, 4. sound absorbing backing, 5. electrical leads, 6. bottom circuit board. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Embodiment 1

[0024] like Figure 1 to Figure 2 As shown, an ultrasonic transducer structure includes a transducer housing 1, a piezoelectric vibrator 2, an acoustic matching layer 3, and a sound absorbing backing 4. The piezoelectric vibrator 2, the acoustic matching layer 3, and the sound absorbing backing 4 are all arranged in the transducer housing 1, and the acoustic matching layer 3, the piezoelectric vibrator 2, and the sound absorbing backing 4 are stacked together in sequence from top to bottom;

[0025] The piezoelectric vibrator 2 transmits and receives signals through the piezoelectric effect between mechanical energy and electrical energy. The piezoelectric vibrator 2 includes a first piezoelectric material layer 21 and a second piezoelectric material layer 22. The first piezoelectric material layer 21 and the second piezoelectric material layer 22 are stacked up and down.

[0026] The acoustic matching layer 3 is interposed between the piezoelectric vibrator 2 and the object to be measured. A bottom circuit board 6 is also disposed in the transducer housing 1 . The sound absorbing backing 4 is interposed between the piezoelectric vibrator 2 and the bottom circuit board 6 .

[0027] Embodiment 2

[0028] In addition to all the technical features of the first embodiment, this embodiment also includes:

[0029] The first piezoelectric material layer 21 and the second piezoelectric material layer 22 constituting the piezoelectric vibrator 2 include, but are not limited to, lead zirconate titanate (PZT) ceramics, lead magnesium niobate-lead titanate (PMN-PT) crystals, lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT) crystals, lead zinc niobate-lead titanate (PZN-PT) crystals, or crystals doped with manganese, iron, cobalt, or samarium elements. It may also be a 1-3 or 2-2 type composite material composed of the above crystals or ceramics and polymer compounds, and the transmission and reception of signals is achieved through the piezoelectric effect between mechanical energy and electrical energy.

[0030] The acoustic matching layer 3 is provided with one or more layers, and the acoustic matching layer 3 is composed of a high molecular polymer or a metal or ceramic composite material of a high molecular weight polymer. The acoustic matching layer 3 is used to minimize the loss of the transmission of the acoustic wave signal. Since the energy transmission of the sound wave between the two media depends on the difference in the acoustic impedance of the two media, the greater the difference, the lower the transmission efficiency. The acoustic impedance value of the piezoelectric material is often greater than the acoustic impedance value of the object under test. Therefore, one or more layers of the acoustic matching layer 3 are required between the piezoelectric material and the object under test to help the transmission of the sound wave energy.

[0031] The sound-absorbing backing 4 is composed of a graphite composite material, a high molecular polymer containing tungsten powder, or a metal composite material. The sound-absorbing backing 4 strongly absorbs and scatters the sound wave energy, so that the sound waves that partially penetrate the piezoelectric vibrator 2 will not interfere with the transmission and reception of the front-end signal by the piezoelectric material due to reflection.

[0032] The bottom circuit board 6 is connected to an electrical lead 5, and the other end of the electrical lead 5 is connected to the host computer / system of the peripheral device for signal transmission. Through the set electrical lead 5, the host computer / system can realize electrical control and feedback of the transducer without affecting acoustic transmission and reception.

[0033] The electrical leads 5 are formed by metal wires, PCB circuit boards or ASIC integrated circuits.

[0034] The first piezoelectric material layer 21 and the second piezoelectric material layer 22 are electrically parallel piezoelectric material layers with opposite polarization directions. The two stacked material layers with opposite polarization directions exponentially increase the capacitance of the piezoelectric vibrator 2, thereby better matching the electrical impedance between the transducer and the system. At the same time, the frequency generated by the total thickness of the stacked piezoelectric crystals is equivalent to the frequency generated by a single piezoelectric crystal, which solves the contradiction between the frequency and capacitance of traditional piezoelectric vibrators.

[0035] Embodiment 3

[0036] like Figures 3 to 6 As shown, an ultrasonic transducer structure, in addition to all the technical features of the first embodiment, also includes:

[0037] Since polarized crystals can be viewed as capacitors, the acoustic stack capacitance can be significantly increased by connecting crystals in parallel. Figure 3 This is a schematic diagram of a single-element transducer, where crystal 1 and crystal 2 have the same height, h / 2, and have the same capacitance C due to their opposite polarization directions. 1。 The capacitance of the stack is given by equation (1):

[0038]

[0039] where ε r is the relative dielectric constant of the crystal, and A is the (001) surface area of ​​the crystal. Figure 4 is a schematic diagram of a conventional single-element transducer, where the height of the crystal 3 is h. The capacitance of the stack is given by equation (2):

[0040]

[0041] Comparing formula (1) and formula (2), we can see that Figure 4 The capacitance in the structure is Figure 3 One-quarter of the capacitance in the structure. At the same time, due to Figure 3 The crystal structure in the same way responds to the excitation voltage Figure 4 The crystal structure is the same as Figure 4 The structure resonates in the same way, so the thickness mode resonant frequency is f A Given by formula (3):

[0042]

[0043] Where v is the speed of sound in the crystal, f B for Figure 4 The thickness mode resonant frequency in .

[0044] By stacking two layers of the same crystal with opposite polarization directions, a transducer can be obtained with the same frequency as a single layer with a thickness equal to the sum of the two layers, while the capacitance of the transducer is increased by a factor of four and the output signal strength is increased.

[0045] Further, the crystals (with an electrically parallel stacked configuration) were used to construct a single-element transducer with a target frequency of 200kHz. In both configurations, a quarter-wavelength layer with a thickness of 2.2mm and an acoustic impedance of 4.8 MRayls was used. The matching layer and a layer with a thickness of 8.0mm and an acoustic impedance of 7.8MRayls The backing layer sandwiches the crystal. The projected area of ​​the transducer is 3.65*3.65mm, which is the size of the element commonly used in 200-300kHz frequency matrix transducers. Figure 5The comparison of -6dB bandwidth, center frequency, and receiving field voltage response (M0) of PMN-PT crystal transducers under different polarization conditions is listed. In terms of -6dB bandwidth, the single-layer (3.4 mm thick PMN-PT) transducer and the stacked (2x1.7 mm thick PMN-PT) transducer achieved 49.0% and 54.2%, respectively. Comparing the single-layer transducer and the stacked transducer, it can be seen that the center frequencies are very similar, confirming that by stacking two layers of the same crystal with opposite polarization directions, the use frequency that can be obtained is the same as the use frequency of the single-layer transducer with the same total thickness. In terms of receiving field voltage response (M 0) In terms of M0, which is a measure of transducer sensitivity, Table 1 shows that the M0 of the single-layer transducer reaches 45.6mV and the M0 of the stacked transducer reaches 143.6mV, an increase of 215% compared to the single-layer transducer. In addition, Figure 6 The time domain received voltage spectra of these two types of transducers are shown. The results show that in different time domains, the received voltage amplitude of the stacked transducer is more than twice that of the single-layer transducer on the same spectrum, which is consistent with the results of the measured M0 value.

[0046] If all processing conditions of the crystal are the same, the excitation voltage is the same and the electrical impedance is perfectly matched, the stacked transducer can achieve approximately twice the received voltage amplitude compared to a single-layer transducer with the same total height, because the PMN-PT crystal responds to twice the electric field and twice the amount of strain. However, considering the limitations of the element size and thickness of the 200kHz transducer, the capacitance of the stacked transducer is 4 times that of the single-layer transducer, which greatly enhances the electrical impedance matching between the transducer and the system, and the stacked transducer responds much better to the excitation signal.

[0047] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0048] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An ultrasonic transducer structure, comprising a transducer housing (1), a piezoelectric vibrator (2), an acoustic matching layer (3), and a sound absorbing backing (4), characterized in that: The piezoelectric vibrator (2), the acoustic matching layer (3) and the sound absorbing backing (4) are all arranged in the transducer housing (1), and the acoustic matching layer (3), the piezoelectric vibrator (2) and the sound absorbing backing (4) are stacked together in sequence from top to bottom; The piezoelectric vibrator (2) transmits and receives signals through the piezoelectric effect between mechanical energy and electrical energy. The piezoelectric vibrator (2) comprises a first piezoelectric material layer (21) and a second piezoelectric material layer (22). The first piezoelectric material layer (21) and the second piezoelectric material layer (22) are stacked up and down. The acoustic matching layer (3) is interposed between the piezoelectric vibrator (2) and the object to be measured, a bottom circuit board (6) is also arranged in the transducer housing (1), and the sound absorbing backing (4) is interposed between the piezoelectric vibrator (2) and the bottom circuit board (6).

2. The ultrasonic transducer structure according to claim 1, characterized in that: The first piezoelectric material layer (21) and the second piezoelectric material layer (22) constituting the piezoelectric vibrator (2) include but are not limited to lead zirconate titanate ceramics, lead magnesium niobate-lead titanate crystals, lead indium niobate-lead magnesium niobate-lead titanate crystals, lead zinc niobate-lead titanate crystals, or crystals doped with manganese, iron, cobalt, or samarium elements, and may also be 1-3 or 2-2 type composite materials composed of the above crystals or ceramics and polymer compounds.

3. The ultrasonic transducer structure according to claim 1, characterized in that: The acoustic matching layer (3) is provided with one or more layers, and the acoustic matching layer (3) is composed of a high molecular polymer or a high molecular polymer metal or ceramic composite material.

4. The ultrasonic transducer structure according to claim 1, characterized in that: The sound absorbing backing (4) is made of a graphite composite material, a high molecular polymer containing tungsten powder, or a metal composite material.

5. The ultrasonic transducer structure according to claim 1, characterized in that: The bottom circuit board (6) is connected to an electrical lead (5), and the other end of the electrical lead (5) is connected to a host computer / system of the peripheral device for signal transmission.

6. The ultrasonic transducer structure according to claim 5, characterized in that: The electrical leads (5) are formed by metal wires, PCB circuit boards or ASIC integrated circuits.

7. The ultrasonic transducer structure according to claim 1, characterized in that: The first piezoelectric material layer (21) and the second piezoelectric material layer (22) are electrically parallel piezoelectric material layers with opposite polarization directions.

Images