Last Updated on June 16, 2021 by You Ling
What is piezoelectric transducer?
The function of the ultrasonic piezoelectric transducer is to convert the input electrical power into mechanical power (ultrasound) and then transmit it out, while consuming a small part of the power by itself.
For the ultrasonic piezoelectric transducer, the technical problem to be solved is to design an ultrasonic piezoelectric transducer with a large working distance and a wide frequency band.
The transducer consists of a shell, a matching layer, a piezoelectric ceramic disc transducer, a backing, a lead-out cable and a Cymbal array receiver. The piezoelectric ceramic disc transducer is made of PZT-5 piezoelectric material polarized in the thickness direction. The Cymbal array receiver consists of 8-16 Cymbal transducers, two metal rings and rubber washers. The working distance of the invention is greater than 35m, the frequency bandwidth reaches 10kHz, and it can detect the long-distance target moving at high speed.
The structure of the ultrasonic piezoelectric transducer
The ultrasonic piezoelectric transducer includes a shell (1), a matching layer or acoustic window (2), a piezoelectric ceramic disc transducer (3), a backing (4), and an outgoing cable (5), which is characterized in that it also includes Cymbal array receiver, which is composed of lead-out cable (6), 8-16 Cymbal transducers (7), metal rings (8), (9) and rubber gasket (10); Cymbal array receiver is located on the disc Above the piezoelectric transducer 3; the piezoelectric ceramic disc transducer is used as the basic ultrasonic piezoelectric transducer, which transmits and receives ultrasonic signals; the Cymbal array receiver is located on the disc piezoelectric transducer, As an ultrasonic receiver, it is used to receive Doppler echo signals outside the frequency band of the disc transducer.
Mainly applicable to ultrasonic plastic welding machine, ultrasonic metal welding machine, ultrasonic cleaning machine, gas camera, trichlorine machine, etc.
Ultrasonic piezoelectric transducers are widely used. According to the application industries, they are divided into industry, agriculture, transportation, life, medical treatment and military. According to the realized functions, it is divided into ultrasonic processing, ultrasonic cleaning, ultrasonic detection, detection, monitoring, telemetry, remote control, etc.; according to the working environment, it is divided into liquid, gas, biological body, etc.; according to the nature, it is divided into power ultrasonic, detection ultrasonic, ultrasonic imaging, etc. .
Piezoelectric ceramic transformer
The piezoelectric ceramic transformer uses the piezoelectric effect of the polarized piezoelectric body to realize the voltage output. The input part is driven by a sinusoidal voltage signal and vibrates through the inverse piezoelectric effect. The vibration wave is mechanically coupled to the output part through the input and output parts. The output part generates electric charge through the positive piezoelectric effect to realize the electric energy of the piezoelectric body. -Mechanical energy-two transformations of electrical energy to obtain the highest output voltage at the resonance frequency of the piezoelectric transformer. Compared with the electromagnetic transformer, this has the advantages of small size, light weight, high power density, high efficiency, breakdown resistance, high temperature resistance, no fear of burning, no electromagnetic interference and electromagnetic noise, and simple structure, easy production, and easy mass production. In some areas, it has become an ideal substitute for electromagnetic transformers and other advantages. This type of transformer is used in switching converters, notebook computers, neon lamp drivers, etc.
Ultrasonic motors use the stator as a transducer, use the inverse piezoelectric effect of the piezoelectric crystal to make the motor stator vibrate at an ultrasonic frequency, and then rely on the friction between the stator and the rotor to transfer energy and drive the rotor to rotate. Ultrasonic motors have small size, large torque, high resolution, simple structure, direct drive, no brake mechanism, no bearing mechanism, these advantages are beneficial to the miniaturization of the device. Ultrasonic motors are widely used in the fields of optical instruments, lasers, semiconductor microelectronics processes, precision machinery and instruments, robotics, medicine and bioengineering.
The mechanism of ultrasonic cleaning is to use physical effects such as cavitation, radiation pressure, and acoustic flow when ultrasonic waves propagate in the cleaning solution, which can peel off the dirt on the cleaning parts, and at the same time can promote the chemical reaction between the cleaning solution and the dirt. Respond to achieve the purpose of cleaning objects. The frequency used by the ultrasonic cleaning machine can be selected from 10 to 500 kHz according to the size and purpose of the cleaning object, generally 20 to 50 kHz. As the frequency of ultrasonic piezoelectric transducers increases, Langevin vibrators, longitudinal vibrators, thickness vibrators, etc. can be used. In terms of miniaturization, there are also radial and flexural vibrations that use disc vibrators. Ultrasonic cleaning has been widely used in various industries, such as industry, agriculture, household equipment, electronics, automobiles, rubber, printing, airplanes, food, hospitals, and medical research.
There are two types of ultrasonic welding: ultrasonic metal welding and ultrasonic plastic welding. Among them, ultrasonic plastic welding technology has been widely used. It uses the ultrasonic vibration generated by the transducer to transmit the ultrasonic vibration energy to the welding area through the upper weldment. Due to the large acoustic resistance of the welding zone, that is, the junction of the two weldments, local high temperature will be generated to melt the plastic, and the welding work will be completed under the action of contact pressure. Ultrasonic plastic welding can facilitate welding of parts that cannot be welded by other welding methods. In addition, it also saves expensive mold costs for plastic products, shortens processing time, improves production efficiency, and is economical, fast, and reliable.
The fine abrasive is applied to the workpiece with a certain static pressure together with the ultrasonic processing tool, and the same shape as the tool can be processed. During processing, the transducer needs to produce an amplitude of 15-40 microns at a frequency of 15-40 kHz. The ultrasonic tool makes the abrasive on the surface of the workpiece continuously impact with considerable impact force, destroying the ultrasonic radiation part, breaking the material and achieving the purpose of removing the material. Ultrasonic processing is mainly used in the processing of brittle and hard materials such as gems, jade, marble, agate, and cemented carbide, as well as the processing of special-shaped holes and fine deep holes. In addition, when the ultrasonic piezoelectric transducer is added to the ordinary cutting tool to vibrate, it can also play a role in improving the accuracy and efficiency.
Ultrasound weight loss
Using the cavitation effect and micro-mechanical vibration of the ultrasonic piezoelectric transducer, the excess fat cells under the human epidermis are crushed, emulsified, and discharged out of the body to achieve the purpose of weight loss and shaping. This is a new technology developed in the 1990s internationally. Zocch i from Italy used ultrasonic degreasing for the bed for the first time and was successful, setting a precedent for plastic surgery and beauty. Ultrasonic fat removal technology has developed rapidly at home and abroad.
Applying appropriate frequency and intensity of ultrasonic irradiation to plant seeds can increase the germination rate of seeds, reduce the rate of mildew, promote the growth of seeds, and increase the growth rate of plants. According to information, ultrasound can increase the growth rate of some plant seeds by 2 to 3 times.
Blood Pressure Monitor
The ultrasonic piezoelectric transducer is used to receive the pressure of the blood vessel. When the airbag compresses the blood vessel, because the applied pressure is higher than the vasodilation pressure, the ultrasonic piezoelectric transducer cannot feel the pressure of the blood vessel; and when the airbag gradually deflates, the ultrasonic piezoelectric transducer When the pressure of the blood vessel decreases to a certain value, the pressure of the two reaches equilibrium. At this time, the ultrasonic piezoelectric transducer can feel the pressure of the blood vessel. This pressure is the systolic pressure of the heart. The blood pressure value. Because the electronic sphygmomanometer eliminates the stethoscope, the labor intensity of medical staff can be reduced.
Telemetry and remote control
In harsh environments such as poisonous and radioactive, people cannot get close to work and need to be controlled remotely; electrical switches such as televisions, electric fans, and lights need to be remotely controlled, and ultrasonic piezoelectric transducers can be installed, and ultrasonic waves can be transmitted remotely. The receiving transducer on the control system converts the acoustic signal into an electrical signal to make the switch act.
In modern transportation, it is very necessary to automatically monitor the passing and counting of vehicles in order to grasp the operating conditions of vehicles. For example, a traffic supervision station is equipped with an ultrasonic piezoelectric transducer and its auxiliary equipment for both transceivers. When a vehicle passes by, a sound pulse returns. The number of daily vehicles can be obtained by counting and accumulating. Install a transmitter-receiver transducer at the rear of the car to prevent a reversing collision. The installation of receiving piezoelectric ultrasonic piezoelectric transducers on the highway can also monitor the noise index.
Ultrasonic distance measuring device is also called sound ruler. It measures the pulse time interval through a transceiver with dual purpose. The sound bar can measure the distance within 10m, and the accuracy can reach a few thousandths.
Leak detection and gas detection
For pressure systems, at leaks, jet noise is caused by the pressure difference between the inside and outside of the pressure vessel. This noise spectrum is extremely wide. For non-pressure systems, an ultrasonic source can be placed in a closed system and then received from outside the closed system. Generally, the measured signal amplitude is very small or no when there is no leakage, and the signal amplitude tends to increase suddenly at the leakage point. Gas flow detection is also one of the important methods in chemical industry. There are a variety of amplifications for flow detection, such as float flowmeters and so on. But the main advantage of using an ultrasonic piezoelectric transducer is that it does not hinder the flow of fluid.
To realize functions such as freely walking in space and recognizing objects, intelligent robots must not only use ultrasonic piezoelectric transducers for distance measurement and guidance, but also imaging recognition. Therefore, a small ultrasonic piezoelectric transducer array is needed to achieve multiple functions. This aspect will become an important research topic, attracting many scientists to fight for it.