CN109701857B - Micro-broadband power ultrasonic transducer adapting to frequency drift - Google Patents

Abstract

The invention relates to the technical field of ultrasonic transducers, in particular to a micro-broadband power ultrasonic transducer adapted to frequency drift. It solves the technical problem that the frequency of the current ultrasonic transducer drifts with the change of external conditions, so that the output power and amplitude cannot be guaranteed. In the invention, the back cover plate, the first group of piezoelectric ceramic crystal stacks, the middle cylinder, the second group of piezoelectric ceramic crystal stacks and the front cover plate are connected together by pre-tightening double-ended studs and nuts. Two piezoelectric ceramic stacks are designed in series. Two piezoelectric ceramic stacks are connected to frequency sources with similar but different frequency values. The invention inputs different frequencies to the two groups of piezoelectric ceramic crystal stacks, which not only widens the frequency band of the transducer but also ensures the output power and amplitude of the transducer. Aiming at the amplitude attenuation caused by the frequency drift, the present invention avoids the detuning caused by the frequency drift on the premise of not affecting the output power basically, and ensures the normal use of the transducer.

Description

Micro-Broadband Power Ultrasonic Transducer Adapting to Frequency Drift

technical field

The invention relates to the technical field of ultrasonic transducers, in particular to a micro-broadband power ultrasonic transducer adapted to frequency drift.

Background technique

The ultrasonic transducer is the energy converter and the key to the entire vibration system. As the core device of ultrasonic technology, the transducer can perform the mutual conversion of mechanical energy, electrical energy and sound energy. The transducer converts the input high-frequency electrical energy into high-frequency vibration mechanical energy through the piezoelectric effect of the piezoelectric material, and generates ultrasonic waves. Due to the various beneficial interactions between ultrasonic waves and substances, power ultrasonics are widely used in ultrasonic cleaning, ultrasonic welding and various ultrasonic machining such as turning, grinding, drilling, finishing and other fields. Ultrasonic cleaning uses the effect of ultrasonic cavitation to quickly remove the surface dirt of objects immersed in liquid. For structures that are not easy to clean, such as deep holes and slits, ultrasonic cleaning can also achieve better cleaning results. Compared with Process cleaning, ultrasonic cleaning has high working efficiency, reduces environmental pollution, and the cleaning effect is more thorough, and does not damage the cleaned objects. Ultrasonic welding uses ultrasonic vibration and cavitation pressure and high temperature effects to promote the mutual diffusion of two substances. It is characterized by no need for flux and external heating, no deformation due to heat, and no residual stress. Not too demanding. Ultrasonic machining uses ultrasonic high-frequency vibration, a new processing method formed by applying ultrasonic vibration in traditional turning, grinding, drilling and other processing processes. Ultrasonic machining reduces cutting force, increases tool life, and improves machining accuracy. Power ultrasonic processing requires ultrasonic transducers to generate high-intensity, high-power ultrasonic waves with high energy transmission efficiency and large vibration displacement.

Only when the power ultrasonic transducer works at the resonant frequency (that is, the system is in a resonance state) can it operate efficiently and obtain the maximum vibration displacement. In practical applications, the frequency of the power ultrasonic transducer changes with changes in external conditions and processing conditions (such as changes in processing temperature, environment, component aging, load, etc.), and the system frequency will drift, causing the replacement of The working frequency of the transducer is deviated from the vicinity of the resonant frequency, which affects the vibration of the transducer and the processing system, and the amplitude of the vibration of the system is also attenuated, and even the phenomenon of stop vibration occurs. For the frequency drift in power ultrasonic machining, most of the current research is to solve it by frequency tracking and optimization of the matching network, but the frequency drift is a dynamic process, and the real-time performance and accuracy of such methods need to be improved.

Prior art related to the present invention

The technical solution of the prior art

Existing methods all use a reasonable matching network and automatic frequency tracking, so that the frequency output by the ultrasonic power source changes with the frequency of the transducer, such as documents 1, 2, 3 and patent 1.

Disadvantages of prior art one

It is difficult to achieve real-time tracking only with dynamic frequency tracking. When the external load of power ultrasonic processing changes rapidly or the temperature rises rapidly, it is difficult to change the frequency of the ultrasonic power supply quickly, which is very easy to cause. Damage to the transducer.

Prior art two related to the present invention

The technical solution of the existing technology 2

Patent 2

A series composite structure dual-frequency, multi-amplitude piezoelectric ultrasonic transducer is proposed for the thermosonic wire bonding and sealing process of integrated circuit chips. The purpose is to achieve various amplitude outputs and the two ends of the transducer vibrate respectively. , the input frequency is 60KHz and 120KHz, and the input frequency is the same when working at the same time.

Disadvantages of prior art two

When excited at the same time, both ends will vibrate, and the energy loss is large. In addition, in this technical solution, when the two groups of piezoelectric ceramic sheets are excited at the same time, the excitation signal of the same frequency is passed, and the vibration form is that the two ends vibrate respectively. The left and right transducers are independent. When connected together, an additional connection surface is added in the middle, which will increase the energy loss at the connection.

Three prior art related to the present invention

The technical solution of the existing technology three

Patent 3

A high-power ultrasonic transducer is provided. The transducer includes a first transducer and a second transducer, the positive and negative poles of the two transducers are connected in parallel, and the resonance frequencies are the same.

Disadvantages of the existing technology three

The resonant frequency is the same, and the input frequency is also the same. The purpose of this technology is to increase the power, and the effect is basically similar to that of a piezoelectric ceramic transducer using the same number of piezoelectric ceramic sheets.

The aforementioned references are as follows:

Literature 1: Du Jinchao. Automatic tracking of ultrasonic transducer resonance frequency based on minimum voltage method [J]. Applied Acoustics, September 2013, Issue 5.

Literature 2: Zhong Long. Design and Research of Ultrasonic Power Supply Based on Dynamic Impedance Matching [D]. Beijing Jiaotong University. 2015.

Literature 3: Li Xialin. Research on fuzzy control algorithm for automatic tracking of ultrasonic power frequency [J]. Applied Acoustics, March 2017, Issue 2.

Patent 1: Tsinghua University. Broadband multi-frequency power amplifier based on multi-impedance zero-point intermodulation matching network. China 201710757007.1 2017.08 CN107528548A.

Patent 2: Zhang Hongjie. A series composite structure dual-frequency multi-amplitude piezoelectric ultrasonic transducer. China 201711389271.02017. 12 CN108176574A.

Patent 3: Chen Yuanping. Tandem high-power transducer. China 201220035353.1 2012.02CN202460960U.

SUMMARY OF THE INVENTION

The invention provides a micro-broadband power ultrasonic transducer adapting to frequency drift in order to solve the technical problem that the frequency of the current ultrasonic transducer drifts with the change of external conditions, so that the output power and amplitude cannot be guaranteed.

The invention is realized by adopting the following technical solutions: a micro-broadband power ultrasonic transducer adapting to frequency drift, comprising a rear cover plate, a first group of piezoelectric ceramic crystal stacks, a middle cylinder, Two groups of piezoelectric ceramic crystal stacks and the front cover plate; it also includes passing through the center of the rear cover plate, the first group of piezoelectric ceramic crystal stacks, the middle cylinder and the second group of piezoelectric ceramic crystal stacks in sequence and screwed into the front cover plate and then screwed into the center of the front cover. A stud connecting the above components; the part of the stud outside the rear cover is screwed with a nut; the stud and the rear cover, the first group of piezoelectric ceramic crystal stacks, the middle cylinder, the second Insulation connection between groups of piezoelectric ceramic crystal stacks;

The first group of piezoelectric ceramic crystal stacks includes two annular copper electrodes whose axes coincide with the axes of the double-ended studs and are arranged in parallel with a certain interval, and piezoelectric ceramics are stacked between the two copper electrodes; The copper electrode is used as the negative electrode, and the copper electrode close to the middle cylinder is used as the positive electrode; piezoelectric ceramics are also stacked between the copper electrode as the positive electrode and the middle cylinder; Two annular copper electrodes arranged in parallel at a certain interval and piezoelectric ceramics stacked between the two copper electrodes; the copper electrode near the middle cylinder is used as the negative electrode, the copper electrode near the front cover plate is used as the positive electrode, and the positive electrode is used as the positive electrode. Piezoelectric ceramics are laminated between the copper electrodes and the front cover; the negative electrodes of the first group of piezoelectric ceramic crystal stacks are connected with the negative electrodes of the second group of piezoelectric ceramic crystal stacks; the positive and negative electrodes of the first group of piezoelectric ceramic crystal stacks are connected The voltage frequency of the positive and negative electrodes of the second group of piezoelectric ceramic crystal stacks is different but similar to the input voltage frequency of the first group of piezoelectric ceramic crystal stacks.

The purpose of the device of the present invention is to provide a power type piezoelectric ultrasonic transducer with a certain frequency conversion function. It has the ability to adapt to certain frequency changes. In the case of using the same number of piezoelectric ceramic sheets, the present invention designs to slightly widen the effective working frequency band of the power ultrasonic transducer, which not only solves the problem of amplitude attenuation caused by frequency changes, but also reduces the frequency of the piezoelectric ultrasonic transducer device. Output power and displacement have little effect. Because it is difficult for ordinary power ultrasonic transducers to work at the resonant frequency due to changes in load, etc., most of them work near the resonant frequency, the effective working frequency range is very small, and the amplitude is difficult to reach the ideal value. The design of the present invention is also guaranteed. When the output amplitude is required, the effective working frequency range is expanded, that is, the working frequency band is slightly widened under the premise of ensuring the output requirements of the power transducer.

The ultrasonic power source used in the present invention should be able to generate two similar frequencies, which are respectively applied to the electrode pieces of the first group of piezoelectric ceramic crystal stacks and the second group of piezoelectric ceramic crystal stacks, so that the two piezoelectric ceramic crystal stacks vibrate simultaneously , the power and amplitude of the two vibrations are superimposed. The designed power ultrasonic transducer nodal surface is located on the middle cylinder, so that the rear end of the transducer is composed of the first group of piezoelectric ceramic crystal stacks, the back cover and part of the middle cylindrical section to form a quarter-wavelength transducer, and It is used as the back cover of the transducer composed of the second group of piezoelectric ceramic crystal stacks. The front end of the transducer is also a quarter-wavelength transducer, which is composed of a second group of piezoelectric ceramic crystal stacks, a front cover plate and a part of the middle cylindrical section. Since the resonant frequencies of the front and rear transducers are close, the wavelengths are almost equal, and the design can be designed according to the equal wavelengths of the front and rear sections of the section.

The working principle of the composite ultrasonic transducer device of the present invention is as follows: the ultrasonic power supply outputs a high-frequency signal, which is transmitted to the first group of piezoelectric ceramic crystal stacks, and another output high-frequency signal is transmitted to the second group of piezoelectric ceramic crystal stacks, so that the The axially polarized piezoelectric ceramic sheets generate ultrasonic stretching vibrations along the device axis. The longitudinal displacement output by the transducer is the superposition of the vibration displacement of the two piezoelectric ceramic stacks. The input signal frequency difference between the two piezoelectric ceramic stacks is very small, so the effect of superposition of the amplitudes at the peak is obvious. Different frequencies can slightly broaden the frequency of vibration, thereby avoiding the amplitude attenuation caused by the frequency drift of the ultrasonic vibration system. The resonance of the two piezoelectric ceramic stacks and the system is achieved by adjusting the lengths of the rear cover plate, the middle cylinder and the front cover plate.

This scheme starts from the design of the transducer itself, and under the premise of ensuring the output power and amplitude of the transducer, the piezoelectric ceramic sheets of the transducer are divided into the same two groups, separated by a cylinder in the middle, and formed near the resonant frequency A transducer that can slightly widen the resonant frequency band to solve the frequency drift caused by changes in external temperature and environment. Formally equivalent to two piezoelectric transducers connected in series. Combined with the frequency tracking of the ultrasonic power source, the transducer of this solution can better ensure the use effect of the power ultrasonic transducer.

Further, the ceramic sheets and copper electrode sheets in the first group of piezoelectric ceramic crystal stacks and the second group of piezoelectric ceramic crystal stacks are subjected to vacuum cold welding treatment before being assembled into the transducer.

Due to the low tensile strength of piezoelectric ceramics, in order to avoid damage to piezoelectric ceramics under high power conditions, it is necessary to increase prestress to ensure that piezoelectric ceramics are always in a compressed state when the transducer vibrates. At the same time, the prestress should not be too large, so as not to hinder the longitudinal vibration of the transducer and cause heat damage to the piezoelectric ceramic sheet. The exact value of the applied preload is often not easy to obtain through calculation and simulation, and needs to be obtained through experiments. After the piezoelectric ceramic stack is vacuum pressure welded, there is a certain connection force between the piezoelectric ceramic sheet and the copper electrode, so the requirement for the preload force applied to the transducer is reduced, and the threshold range of the applied preload force is expanded. The applied prestress value is reduced, and the damage of piezoelectric ceramics caused by improper prestressing is greatly reduced.

Further, the studs are prestressed studs.

The prestressed double-ended stud and the nut cooperate to provide the prestress required for the axial vibration of the first group of piezoelectric ceramic crystal stacks and the second group of piezoelectric ceramic crystal stacks.

The innovation of the present invention is as follows:

(1) The ultrasonic transducer of the present invention adopts two transducers in series, and the number and shape of the piezoelectric ceramic sheets used in the two groups of piezoelectric ceramic crystal stacks are the same;

(2) Both sets of transducers are quarter-wavelength;

(3) The first group of piezoelectric ceramic crystal stacks and the second group of piezoelectric ceramic crystal stacks are connected by an intermediate cylinder, and prestress is applied together, and there is one less connection surface than two separate transducers connected together;

(4) The prestressed stud and the nut cooperate to provide the prestress required for the axial vibration of the first group of piezoelectric ceramic crystal stacks and the second group of piezoelectric ceramic crystal stacks;

(5) The ceramic sheets and copper electrode sheets in the first group of piezoelectric ceramic crystal stacks and the second group of piezoelectric ceramic crystal stacks should be connected by vacuum cold pressure welding;

(6) The copper electrodes in the first group of piezoelectric ceramic stacks are connected to the low-frequency output wiring of the ultrasonic power supply, and the ultrasonic energy is converted into axial ultrasonic mechanical energy during operation; the copper electrodes in the second group of piezoelectric ceramic stacks are connected to The other high-frequency output wire of the ultrasonic power supply is connected, and the ultrasonic frequency electric energy is converted into axial ultrasonic frequency mechanical energy during operation;

(7) The two transducers connected in series are connected to different but similar frequencies (two different frequencies output by the same ultrasonic generator) to ensure that the power and amplitude of the transducer output are not substantially reduced when the resonant frequency range is widened. .

Beneficial effects brought about by the technical solution of the present invention

(1) The device of the present invention connects two sets of piezoelectric ceramic crystal stacks in series to form a composite ultrasonic transducer, and inputs different frequencies (not much difference) to the two sets of piezoelectric ceramic crystal stacks, which not only broadens the frequency band of the transducer Moreover, the output power and amplitude of the transducer are guaranteed. Aiming at the amplitude attenuation caused by the frequency drift, the present invention starts from the design of the transducer itself, avoids the detuning caused by the frequency drift on the premise of not affecting the output power basically, and ensures the normal use of the transducer;

(2) The piezoelectric ceramic crystal stack in the device of the present invention is subjected to vacuum cold welding treatment before assembling the transducer, which avoids to a certain extent the damage to the transducer caused by the improper application of the pre-tightening force; After the vacuum welding process between the electric ceramic sheet and the copper electrode, the threshold range of the prestress applied to the transducer is expanded, which effectively increases the service life of the piezoelectric ceramic sheet and greatly reduces the damage caused by the improper prestress value applied. cause damage to the piezoelectric ceramic sheet;

(3) The piezoelectric ceramic sheets are divided into two groups, so that the power and voltage required by each group are reduced, thereby reducing the heat generation of the transducer and improving the energy conversion efficiency of the transducer. In addition, due to the reduction of the number of ceramics in the piezoelectric ceramic stack, the heat dissipation of the ceramic sheet is easy to avoid the heat damage of the piezoelectric ceramics;

(4) The two groups of piezoelectric ceramic crystal stacks are connected by double-ended studs to apply prestressing force, and the structure of applying prestressing force is simple and effective.

Description of drawings

Figure 1 is the overall structure diagram of the series power transducer;

Figure 2 is a diagram of the internal structure of the series power transducer (cross-section);

Figure 3 is a schematic diagram of the connection structure of the front and rear ceramic stacks (the electrode relationship and the connection relationship between the two groups are indicated).

1- Rear cover plate, 2- The first group of piezoelectric ceramic crystal stack, 3- Middle cylinder, 4- The second group of piezoelectric ceramic crystal stack, 5- Front cover plate, 6- Double-ended stud, 7- Nut, 8- Insulation sleeve, 9- Piezoelectric ceramic, 10- Copper electrode.

Detailed ways

The rear cover plate 1 , the first group of piezoelectric ceramic crystal stacks 2 , the middle cylinder 3 , the second group of piezoelectric ceramic crystal stacks 4 and the front cover plate 5 are connected together by preloading studs and nuts 7 . One end of the pre-tightening double-ended stud screwed into the front cover plate 5 is completely screwed in according to the standard, and the other end is connected with the nut;

The ceramic sheets and copper electrode sheets in the first group of piezoelectric ceramic crystal stacks 2 should be connected by vacuum cold pressure welding, and then enter the assembly of the transducer;

The ceramic sheets and copper electrode sheets in the second group of piezoelectric ceramic crystal stacks 4 should be connected by vacuum cold pressure welding, and then enter the assembly of the transducer;

The copper electrodes in the first group of piezoelectric ceramic crystal stacks 2 are connected with the low-frequency output wires that generate ultrasonic power, and convert ultrasonic energy into axial ultrasonic mechanical energy during operation;

The copper electrodes in the second group of piezoelectric ceramic crystal stacks 4 are connected to the slightly higher frequency output wires of the ultrasonic power supply, and during operation, the ultrasonic frequency electric energy is converted into axial ultrasonic frequency mechanical energy;

The first group of piezoelectric ceramic crystal stacks 2 and the second group of piezoelectric ceramic crystal stacks 4 are connected in parallel on the circuit, and the number of piezoelectric ceramic sheets in the two piezoelectric ceramic crystal stacks is the same;

The prestressed stud and the nut 7 cooperate to provide the prestress required for the axial vibration of the first group of piezoelectric ceramic crystal stacks 2 and the second group of piezoelectric ceramic crystal stacks 4;

An insulating sleeve 8 is installed between the prestressed double-ended stud and the piezoelectric ceramic crystal stack 2 , the middle cylinder 3 , and the second group of piezoelectric ceramic crystal stacks 4 ;

The rear cover plate 1 , the first group of piezoelectric ceramic crystal stacks 2 , the middle cylinder 3 , the second group of piezoelectric ceramic crystal stacks 4 and the front cover plate 5 have the same outer diameter.

The ultrasonic power source used in this scheme should be able to generate two similar frequencies, such as 19.8KHz and 20KHz, which should be applied to the electrodes of the first group of piezoelectric ceramic crystal stacks 2 and the second group of piezoelectric ceramic crystal stacks 4 respectively, so that the The two ceramic stacks vibrate at the same time, and the power and amplitude of the two vibrations are superimposed.

In practical applications, the number of piezoelectric ceramics (piezoelectric sheets) in the first and second groups of piezoelectric ceramic stacks is not limited to two, but can also be four, six, etc.; between adjacent piezoelectric ceramics With copper electrodes.

The power ultrasonic transducer designed in this scheme is one-half wavelength, and the nodal surface is selected on the middle cylinder during design. The form is two quarter-wavelength transducers connected in series, as shown in Figure 1, the dotted line represents the power conversion The nodal position of the energy device (the specific position is calculated according to the design requirements). Taking the nodal plane as the boundary, it can be regarded as two quarter-wavelength transducers connected in series, and the rear transducer (the part including the first group of piezoelectric ceramic crystal stacks in the figure) is used as the front transducer (the figure includes Part of the second group of piezoelectric ceramic crystal stacks) part of the back cover, correspondingly the front transducer is used as the front cover of the rear transducer part. The rear transducer is connected to the low frequency output interface of the ultrasonic power supply, and the front transducer is connected to the high frequency output interface of the ultrasonic power supply. The two output frequency values of the ultrasonic power supply are determined according to the frequency bandwidth corresponding to the output amplitude that the transducer needs to achieve. The frequency difference corresponding to this bandwidth is the two frequency difference output by the ultrasonic power supply. Since the amplitude of the transducer only reaches the maximum at the resonant frequency, the effective working frequency range is very small, that is, the working frequency band is very narrow, so the frequency difference between the two groups of transducers should be small, and the difference will affect the output power and amplitude.

The first group of piezoelectric ceramic crystal stacks 2 and the second group of piezoelectric ceramic crystal stacks 4 are connected by a middle cylinder, and prestressing is applied together, and there is one less connection surface than when separate transducers are connected together, so that energy transmission loss is lost. less, which facilitates the application of prestress.

In the design, the resonant frequencies of the front and rear two groups of transducers are satisfied by adjusting the length of each section. First, according to the existing frequency equation, design the size of each section corresponding to the resonance of the quarter-wave transducer where the first group of piezoelectric ceramic stacks is located, and then surround the quarter-wave transducer where the second ceramic stack is located. Design the length of the middle cylinder section and the front cover plate according to the frequency equation.

The technical key points of the present invention:

(1) Connect the first group of piezoelectric ceramic crystal stacks 2 and the second group of piezoelectric ceramic crystal stacks 4 in series;

(2) The prestressed stud and the nut 7 cooperate to provide the prestress required for the axial vibration of the first group of piezoelectric ceramic crystal stacks 2 and the second group of piezoelectric ceramic crystal stacks 4;

(3) The two transducers are connected to different frequency sources but the frequency values should be similar;

(4) The number and shape of piezoelectric ceramic sheets used in the first group of piezoelectric ceramic crystal stacks 2 and the second group of piezoelectric ceramic crystal stacks are the same, and the middle is connected by a cylinder;

(5) The first group of piezoelectric ceramic crystal stacks 2 and the second group of piezoelectric ceramic crystal stacks 4 are subjected to vacuum cold welding before being assembled into the transducer.

Protection point of the present invention:

(1) The two input frequencies should be relatively close, so that the output power is less affected, and the resonance frequency band can be slightly broadened;

(2) Two sets of piezoelectric ceramic crystal stacks apply pre-tightening force through the cooperation of double-ended studs and nuts;

(3) The piezoelectric ceramic crystal stack should be subjected to vacuum cold welding before assembling the transducer;

(4) The first group of piezoelectric ceramic crystal stacks and the second group of piezoelectric ceramic crystal stacks are connected by an intermediate cylinder, and prestressing is applied together.

Claims (10)

1. A frequency drift adaptive micro-broadband power ultrasonic transducer is characterized by comprising a rear cover plate (1), a first group of piezoelectric ceramic crystal stacks (2), a middle cylinder (3), a second group of piezoelectric ceramic crystal stacks (4) and a front cover plate (5), which are coaxially and tightly pressed and arranged in sequence; the piezoelectric ceramic material also comprises a rear cover plate (1), a first group of piezoelectric ceramic crystal piles (2), a middle cylinder (3) and a second group of piezoelectric ceramic crystals which penetrate through the rear cover plate in sequence

The double-end stud (6) is arranged at the center of the ceramic crystal stack (4) and screwed into the front cover plate (5) to connect the components; a nut (7) is screwed on the part of the stud (6) outside the rear cover plate (1); the double-end stud (6) is in insulated connection with the rear cover plate (1), the first group of piezoelectric ceramic crystal piles (2), the middle cylinder (3) and the second group of piezoelectric ceramic crystal piles (4); the first group of piezoelectric ceramic crystal piles (2) comprises two annular copper electrodes (10) which are overlapped with the axis of the stud (6) at intervals and arranged in parallel, the two copper electrodes of the first group of piezoelectric ceramic crystal piles (2) are used as a first group of copper electrodes, and piezoelectric ceramic (9) is laminated between the two first group of copper electrodes; the copper electrode close to the rear cover plate (1) in the first group of copper electrodes is used as a negative electrode, and the copper electrode close to the middle cylinder (3) is used as a positive electrode; piezoelectric ceramics (9) are laminated between the copper electrode as the anode and the middle cylinder (3); the second group of piezoelectric ceramic crystal stacks (4) comprises two annular copper electrodes (10) and piezoelectric ceramic (9), wherein the axes of the two annular copper electrodes are superposed with the axis of the stud (6) and are arranged in parallel at intervals, and the piezoelectric ceramic (9) is laminated between the two copper electrodes (10); two copper electrodes of the second group of piezoelectric ceramic crystal stacks (4) are used as a second group of copper electrodes, a copper electrode (10) close to the middle cylinder (3) in the second group of copper electrodes is used as a negative electrode, a copper electrode close to the front cover plate (5) is used as a positive electrode, and piezoelectric ceramics (9) are laminated between the copper electrode used as the positive electrode and the front cover plate (5); the negative electrode of the first group of piezoelectric ceramic crystal stacks (2) is connected with the negative electrode of the second group of piezoelectric ceramic crystal stacks (4); the positive and negative electrodes of the first group of piezoelectric ceramic crystal piles (2) input voltage with certain frequency, and the voltage frequency input by the positive and negative electrodes of the second group of piezoelectric ceramic crystal piles (4) is different from but close to the input voltage frequency of the first group of piezoelectric ceramic crystal piles (2).

2. The frequency-drift-adaptive micro-broadband power ultrasonic transducer according to claim 1, wherein the rear end of the transducer is a quarter-wave transducer consisting of a first group of piezoelectric ceramic crystal stacks (2), a rear cover plate (1) and a part of an intermediate cylindrical section, and is used as a rear cover plate of a transducer consisting of a second group of piezoelectric ceramic crystal stacks (4); the front end of the transducer is also composed of a quarter-wavelength transducer consisting of a second group of piezoelectric ceramic crystal stacks (4), a front cover plate (5) and a part of middle cylindrical section.

3. The frequency-drift-adaptive micro-broadband power ultrasonic transducer according to claim 1 or 2, wherein the piezoelectric ceramics (9) and the copper electrodes (10) in the first group of piezoelectric ceramic crystal stacks (2) and the second group of piezoelectric ceramic crystal stacks (4) are subjected to a vacuum cold welding process before being assembled into the transducer.

4. The frequency-drift-adaptive micro-broadband power ultrasonic transducer according to claim 1 or 2, wherein the stud (6) is a prestressed stud.

5. The frequency-drift-adaptive micro-broadband power ultrasonic transducer according to claim 3, wherein the stud (6) is a prestressed stud.

6. The frequency-drift-adaptive micro-broadband power ultrasonic transducer according to claim 1 or 2, wherein the number of piezoelectric ceramic plates in the two piezoelectric ceramic crystal stacks is the same.

7. The frequency-drift-adaptive micro-broadband power ultrasonic transducer according to claim 1 or 2, wherein the positive and negative electrodes of the first group of piezoelectric ceramic crystal stacks (2) are connected with a low-frequency output connecting line for generating an ultrasonic power supply, the input voltage frequency is 19.8KHz, the positive and negative electrodes of the second group of piezoelectric ceramic crystal stacks (4) are connected with a slightly high-frequency output connecting line for generating an ultrasonic power supply, and the input voltage frequency is 20 KHz; the ultrasonic power supply is the same device and the device outputs two frequencies.

8. The frequency-drift-adaptive micro-broadband power ultrasonic transducer according to claim 3, wherein the positive and negative electrodes of the first group of piezoelectric ceramic crystal stacks (2) are connected with a low-frequency output connection line for generating an ultrasonic power supply, the input voltage frequency is 19.8KHz, the positive and negative electrodes of the second group of piezoelectric ceramic crystal stacks (4) are connected with a slightly high-frequency output connection line for generating an ultrasonic power supply, and the input voltage frequency is 20 KHz; the ultrasonic power supply is the same device and the device outputs two frequencies.

9. The frequency-drift-adaptive micro-broadband power ultrasonic transducer according to claim 1 or 2, wherein the insulating sleeve (8) is sleeved on the stud (6) at the inner parts of the back cover plate (1), the first group of piezoelectric ceramic crystal stacks (2), the middle cylinder (3) and the second group of piezoelectric ceramic crystal stacks (4).

10. The frequency-drift-adaptive micro-broadband power ultrasonic transducer according to claim 1 or 2, wherein the back cover plate (1), the first group of piezoelectric ceramic crystal stacks (2), the middle cylinder (3), the second group of piezoelectric ceramic crystal stacks (4) and the front cover plate (5) have the same outer diameter.

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