What Is The Working Principle Of "Ultrasonic Transducer"? What Are The Classifications?
Principle of Ultrasonic Transducer:
The ultrasonic transducer is the core component of the ultrasonic welding machine, just like the engine of a car. The ultrasonic transducer converts the high-frequency electrical energy or magnetic energy output by the ultrasonic generator into mechanical vibration of the same frequency. The ultrasonic transducer is divided into two parts. One is a magnetostrictive transducer and the other is a piezoelectric ceramic transducer.
Magnetostrictive transducers, due to their low efficiency and low cost performance, also need an external DC polarized magnetic field, so ultrasonic welding machines have rarely been used at present. Nowadays, ultrasonic welding machines all use piezoelectric ceramic transducers. The fundamental principle is the piezoelectric effect of crystal materials. This material is piezoelectric crystal material. There will be charges, and an electric field will be generated inside the crystal. On the contrary, when the crystal is subjected to an external electric field, the gold sheet will deform. This situation is called the piezoelectric effect. The former is called the positive electric effect or the reverse electric effect.
Ultrasonic transducer classification:
The ultrasonic transducer is the heart of the ultrasonic welding machine. The quality of the ultrasonic transducer design is directly related to the performance, stability and life of the welding machine. Most of the piezoelectric ceramic transducers used in the market are based on vibration. There are many types of differences, such as radial vibration form, longitudinal composite vibration form, shear vibration form, thickness vibration form, etc. When the ultrasonic plastic welding machine welds plastic workpieces, it adopts longitudinal high-frequency vibration. The upper and lower molds of the workpiece are melted under high-frequency vibration and friction, and then welded and formed under the action of pressure, so as to achieve the welding effect.
The structure of the piezoelectric ceramic transducer is composed of piezoelectric ceramic wafers, electrode sheets, front and rear covers, etc. The rear cover is generally made of high-quality steel. The front cover is made of light-weight, high-strength aluminum alloy or titanium alloy. It is a longitudinal effector using piezoelectric ceramics. The polarization direction of the ceramic components The direction of the electric field and the direction of mechanical vibration are different.
1. Most of the ceramic components have a large compressive strength. When the environmental strength changes, the stability of the transducer will change. Due to the defect of the ceramic material, the allowable tensile stress is small, and all ultrasonic waves are affected. Configure overload system to avoid transducer damage when overload occurs.
2. Since the converging part in the middle is composed of a group of electrode shafts on the axially polarized rings at both ends, the maximum effective coupling coefficient can be used.
3. The number of rings and the connection method are optional, so that the transducer can be designed with a wider impedance and frequency range.
4. By changing the material size of the metal cover plates at the head and tail, the performance parameters such as the bandwidth of the transducer, the vibration speed ratio of the front and rear and the effective electromechanical coupling coefficient can be controlled.
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