The ultra-audio electric energy higher than 20KHZ generated by the ultrasonic generator is converted into mechanical vibration with the same frequency by the transducer and introduced into the cleaning solution. The ultrasonic waves alternately propagate forward, generating numerous tiny bubbles, which form and grow in the negative pressure area where the ultrasonic waves propagate longitudinally, and rapidly rupture in the positive pressure area. This process of formation, growth and rapid rupture of tiny bubbles is called "cavitation effect". In the cavitation effect, the instantaneous high pressure of more than 10000 atmospheric pressure is generated after the bubble bursts, and it continues.
Instantaneous high pressure bombards the surface of an object like a series of small explosions, causing the dirt on the surface of the object to fall off quickly.
When ultrasonic waves with a certain intensity are emitted into the liquid medium, the surface of the cleaned object is repeatedly subjected to pressurization and decompression to produce cavitation effect, and tiny cavities appear in the liquid. When the sound wave reaches a certain intensity, the cavity will explode violently, resulting in a strong collision. The pressure is 0.5-50 tons/cm2, and the energy is very large, so that the water will impact the surface of the cleaned object with an acceleration exceeding 10000g, and the dirt will be knocked down. So as to achieve a remarkable cleaning effect, which can achieve liquid cleaning of all surfaces of objects, which can not be achieved by traditional methods such as manual cleaning and mechanical vibration.
Because the cavitation effect will produce sound pressure and thermal effect, it can attack bacteria, especially chain bacteria, and achieve the effect of sterilization and disinfection. In addition, ultrasound has a strong emulsifying effect, which can play the role of uniform stirring, grinding and crushing.
Third, application
In view of the above principles, ultrasonic cleaning can be widely used in all walks of life to achieve the purpose that other cleaning methods are difficult to achieve. Its main applications are as follows:
(1) Cleaning of mechanical parts (especially precision parts): bearings, oil pumps, nozzles, cylinders, mechanical watch cores, automobile parts (without disassembly and cleaning), textile spindles, oil drilling parts (such as gears, cutters, cutters), etc.
(2) Cleaning of optical parts: optical devices and optical fibers.
(4) Cleaning and treatment of electromechanical components: contacts, semiconductor sockets and high-performance electrical connectors.
(5) cleaning the semiconductor chip
(6) Cleaning of printed circuit board
(7) Surface treatment of metal products (such as rust removal, degreasing, phosphating, passivation, etc.). )
(8) Clean all kinds of glass bottles and utensils.
(9) Cleaning of filter
(10) Clean all kinds of seals.
(1 1) noble metal cleaning
(12) Pretreatment before electroplating
(13) Eliminate the blockage of advanced drawing pens.
(14) Cleaning of jade after processing
(15) Dispersion and Ultrafine Treatment of Materials
(16) surface treatment of electric furnace wire after cold drawing
(17) Tableware cleaning
(18) Cleaning of comb holes of nylon spinneret
(19) Cleaning of comb hole of rubber separator of battery
(20) Emulsification of diesel oil and water
Uniform mixing of (2 1) solvents
(22) Wine aging treatment
(23) ultrasonic flotation of seeds
Therefore, ultrasonic technology is widely used in mechanical and electronic industries, metallurgical processing, food processing, medical and health care, light textile, art and fine arts, printing industry, rubber industry, medicine and family fields. In addition, ultrasonic technology can also be used for welding, metal and gem drilling, metal cutting and grinding, and has broad application prospects.
Fourth, product technical analysis
Development of ultrasonic power supply.
In the early 1960s, China began to develop ultrasonic generators (ultrasonic power supplies) with various powers. Up to now, ultrasonic power supply has experienced the development process with electronic tube, thyristor, triode, VMOS and IGBT as switching elements. The generator composed of electron tubes in China was formed in the 1970s. However, the equipment of this power supply has extremely low power utilization rate, high power supply cost and large volume. From the 1970s to the early 1980s, generators with thyristor circuits began to be put into use. Compared with electron tube power supply, this power supply has greatly improved efficiency and reduced volume and weight. However, due to the limitation of switching speed and the influence of thyristor switching characteristics, this power supply generally works below 20KHZ, with high cost, large volume and unsatisfactory working efficiency. At present, there are still many companies that produce and use the above power supply.
In order to reduce the shortage of the above power supply, people began to widely develop and use VMOS power supply. Compared with the crystal three-tube power supply, VMOS unipolar switch tube has fast switching speed and low driving power. Due to the limitation of the manufacturing process and structure of the lamp tube, the single tube has small conduction current, low withstand voltage and poor ability to resist impulse current and impulse voltage. The driving power of transistor is high, so the switching speed of high-power compound transistor will be greatly reduced, and it can only be used below 20KHZ. Therefore, vmosfet and transistor are generally suitable for smaller cleaning machine power supply.
In view of the above characteristics, we adopted a new IGBT device with fast switching speed, large on-current and high withstand voltage, strong impact resistance and low driving power, and combined with modern control technology, developed a high-power and serialized ultrasonic power supply, which greatly improved the performance of the product and greatly reduced the cost. At the same time, it solves the problems caused by the impedance change and center frequency drift of the transducer, and becomes an updated product of ultrasonic power supply.
2. Product structure
Ultrasonic cleaning machine is mainly composed of cleaning tank and ultrasonic power supply, which are connected by cable. A frequency converter is installed below the cleaning tank of the tank cleaner; For immersion cleaning machines, the sensor is sealed in a stainless steel box. The transducer converts the electric energy emitted by the power supply into mechanical waves to achieve the purpose of cleaning.
(1) cleaning tank: stainless steel SUS304 or 3 16L can be used, or special stainless steel can be used for argon arc welding according to specific cleaning process requirements, and it must be absolutely watertight.
(2) Transducer: a vibrating head consisting of a specially made piezoelectric ceramic transducer piece and a metal compact, with high efficiency, long service life and no easy damage. The adhesive is resin glue, which has high temperature resistance, vibration resistance, high strength and prevents falling off.
(3) Ultrasonic generator: the circuit structure is perfect, and the cabinet panel is equipped with power switch, overload indicator, electric meter, etc. According to the needs of users, digital timer can be configured, and digital power indicator and power adjustment circuit can be added.
3. Table of technical characteristics
As a new technology product, the main circuit of ECP series ultrasonic power supply works in the matching resonance state.
The power supply has the following characteristics:
(1) circuit can be easily matched with piezoelectric ceramic transducers with various frequencies and different impedance characteristics.
(2) Wide working frequency range
(3) The single machine has high power, which can reach several kilowatts or more.
(4) The input voltage of power supply is single-phase 220V or three-phase 380V. Using 380V input voltage for high power can ensure the balance of three-phase power grid.
(5) It is convenient for modular design. The cleaning machine with tens of kilowatts or more can be composed of power units with hundreds of watts or several kilowatts, which is beneficial to the optimal assembly of the transducer and ensures that the transducer works in the best state; Meanwhile, each power module has its own protection and tracking system. If one unit fails, other units can still work normally. Damaged units are easy to replace and maintain.
(6) Each IGBT unit can perform rapid overcurrent protection, effectively protecting the switch tube from being damaged.
(7) With frequency feedback circuit and power feedback circuit, the phase relationship between the circuit and voltage can be adjusted and locked, so as to avoid large power fluctuation caused by load impedance changing with environmental temperature, water level and other factors.
(8) The power supply has the ability to limit the maximum power and current, thus reducing the failure rate of the power supply.
(9) Power regulation can be realized.
(10) has the functions of soft start and undervoltage protection.
(1 1) has the functions of quick overload protection and output short circuit protection.
(12) power supply is small in size and light in weight.
(13) High energy efficiency.
(14) power supply can be used not only for ultrasonic cleaning, but also for other ultrasonic application fields, such as ultrasonic welding, ultrasonic drilling and ultrasonic cell crushing.
Ultrasonic transducer: Sandwich structure and bonding pressure make the transducer integrated and work stably and reliably.
4. The main parameters of ultrasonic cleaning:
Frequency: ≥20KHz
Cleaning medium: ultrasonic cleaning, generally two kinds of cleaning agents: chemical solvent, water-based cleaning agent, etc.
The chemical action of cleaning medium can accelerate the effect of ultrasonic cleaning. Ultrasonic cleaning is a physical action, and the two actions are combined to thoroughly clean the object.
Power density: power density = emission power (W)/ emission area (cm2) usually ≥0.3W/cm2. The higher the power density of ultrasonic wave, the stronger the cavitation effect, the faster the speed and the better the cleaning effect. However, for precision objects with high surface finish, long-term high power density cleaning will cause "cavitation" corrosion on the surface of the object.
Ultrasonic frequency: The lower the ultrasonic frequency, the easier it is to generate cavitation in the liquid, and the stronger the acting force, the stronger the effect. Suitable for initial cleaning of workpieces (rough and dirty). If the frequency is high, the ultrasonic wave has strong directivity and is suitable for fine object cleaning.
Cleaning temperature: Generally speaking, ultrasonic wave has the best space-time effect at 30℃-40℃. The higher the temperature of the cleaning agent, the more obvious the effect. Usually, when ultrasonic is used in practice, the working temperature is 50℃-70℃.