The ultrasonic transducer is a sandwich component made of lead zirconate titanate piezoelectric ceramic material. Ultrasonic cleaning machines mostly use a horn-type ultrasonic transducer to increase the coupling and acoustic radiation efficiency by enlarging the radiation surface of the front cover. With proper prestressing, the transducer has good electromechanical conversion efficiency under high power and high amplitude conditions.
one. History of development
At the beginning of the 20th century, the development of electronics enabled people to make various electromechanical transducers using the piezoelectric effect and magnetostrictive effect of certain materials. In 1917, the French physicist Lang Zhiwan made a sandwich ultrasonic transducer using natural piezoelectric quartz and used it to probe submarines on the seabed. With the continuous development of ultrasonic applications in various military and national economic sectors, magnetostrictive transducers with more ultrasonic power, as well as electric, electromagnetic, and electrostatic transducers for various purposes Ultrasonic transducer.
Two. Material classification
Ultrasonic transducers generally have two types of magnetostrictive transducers and piezoelectric crystal transducers.
There are nickel plate transducers and ferrite transducers that are magnetostrictive.
The electro-acoustic conversion efficiency of the ferrite transducer is relatively low, and the efficiency is generally reduced after one or two years of use, and even the electroacoustic conversion capability is almost lost. Nickel plate transducers are complex and expensive, so they are rarely used today.
Piezoelectric crystal type
One of the most mature and reliable is the device that converts electrical energy and acoustic energy by piezoelectric effect, called piezoelectric transducer. The electrical signal is converted to mechanical vibration by the piezoelectric effect of the material. The transducer has high electro-acoustic conversion efficiency, low raw material price, convenient production, and is not easy to age.
Commonly used materials are quartz crystal, barium titanate and lead zirconate titanate. The amount of expansion and contraction of the quartz crystal is too small, and the voltage of 3000 V produces deformation of 0.01 μm or less. The piezoelectric effect of barium titanate is 20-30 times larger than that of quartz crystal, but the efficiency and mechanical strength are not as good as those of quartz crystal. Lead zirconate titanate has the advantages of both, and is generally used as a transducer for ultrasonic cleaning, flaw detection and low-power ultrasonic processing.
1. Central piezoelectric ceramic component 2. Front and rear metal cover 3. Prestressed screw 4. Electrode piece 5. Insulation tube
This sandwich transducer produces stable ultrasonic waves when the load changes, and is the most basic and most important method for obtaining a power ultrasonic driving source.
Four. Ultrasonic transducers have been inspected before leaving the factory.
Use the special vibration head impedance tester to test the main parameters of the vibration head: Fs R1 C0 Qm, and divide the vibration head. The classification rule is that the impedance is ≤25Ω, the impedance difference is within 10Ω, and the frequency is < ±0.5KHz, the difference within 100Hz is the first gear.
Vibration head: 1. There are matching parameters 2. Both are experienced for 3 months, and the function is stable.