The principle of Ultrasonic transducer structureDate: 2022-09-27Number: 221
The Ultrasonic transducer is the source and function of high frequency mechanical vibration for Ultrasonic welding machines. It is to convert the electrical or magnetic energy output from the ultrasonic generator into mechanical vibration of the same frequency. The transducer for Ultrasonic welding machines, there are two kinds at present, one is magnetostrictive transducer, the other is piezoelectric ceramic transducer.
Magnetostrictive transducers are rarely used at present because of their low efficiency, low cost performance and the need for a DC polarized magnetic Ultrasonic welding.
The key to the Ultrasonic welding machine is the production of piezoelectric ceramics. When these materials deform in perfect places, there is an electric charge on the surface of the piezoelectric ceramic crystal, and the internal structure of the crystal generates an electric field, when the crystal under the function of an external electric field, the gold plate will appear deformation, this kind of phenomenon is called piezoelectric effect, the former is called positive phenomenon, or called reverse electric phenomenon.
The Ultrasonic transducer is the key component of the ultrasonic vibration system. The quality of the Ultrasonic transducer design is related to the efficiency, stability and service life of the welding machine, most piezoelectric ceramic transducers are used in the market. There are many kinds of vibration modes, such as radial vibration mode, longitudinal compound vibration mode, shear vibration mode, thickness vibration mode and so on. Ultrasonic plastic welding machine work when processing plastic parts, more need is a high-frequency longitudinal vibration. The welding effect can be obtained by melting the welding layer with high frequency vibration in the upper and lower dies of the workpiece.
Construction of piezoelectric transducer:
The structure of the piezoelectric ceramic transducer is composed of a piezoelectric ceramic chip, an electrode plate, a front and rear left and right cover, etc. . High-strength aluminum or titanium alloys are manufactured using the same longitudinal effect of piezoelectric ceramics, the polarization orientation of the ceramic element, the electric field orientation, and the mechanical vibration orientation. This kind of transducer is called longitudinal compound vibration transducer, whose length and azimuth dimension are much higher than the width of both.
This kind of transducer can control the frequency bandwidth, the ratio of increase speed and the effective electromechanical coupling coefficient by changing the material size of the front, left and right cover. For Ultrasonic welding machines, parameters such as pole resonant frequency (series-parallel) , parallel characteristic impedance, static capacitance, front and velocity ratios are extremely important. The most common front vibration transducer used in Ultrasonic welding machines is a half-wavelength transducer, and a quarter-wavelength transducer is rarely used.
Advantages of piezoelectric ceramic transducers:
Most of the ceramic components have relatively large compressive strength, the central screw provides special use, while at the same time in the environmental strength changes to improve the stability of the transducer, and at the same time to ensure that the original under high-power drive compression state, in this way, the breakage of the ceramic disc curtain due to defects in the ceramic material can be avoided with an acceptable low tensile stress
The number of rings and the connection method are optional, which can be used to design the transducer in a wide range of characteristic impedance and frequency
Changing the material size of the head and tail metal cover plate can control the technical parameters such as the bandwidth of the transducer, the front-to-back left-to-right velocity ratio and the effective electromechanical coupling coefficient