Application of piezoelectric ceramics in the new fields(1)

Views: 1 Author: Site Editor Publish Time: 2019-09-16 Origin: Site

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Since the Curie brothers discovered the piezoelectric effect of tourmaline in 1880, the history of piezoelectrics ceramics began from quartz and BaTiO3, ceramics have played an important role in the history of piezoelectrics. However, after the discovery of PZT piezoelectric ceramics, the speed of applying piezoelectric ceramics has been greatly accelerated, and the application of piezoelectric ceramics has taken on a new situation.

Piezoelectric ceramics are functional ceramic materials that convert mechanical energy and electrical energy to each other and have a piezoelectric effect. The so-called piezoelectric effect refers to the phenomenon that the polarization (or electric field) is induced by stress or the stress (or strain) is induced by the electric field. The former is a positive piezoelectric effect and the latter is a negative piezoelectric effect. Electrical effect. So far, this piezoelectric effect of piezoelectric tube transducer has been applied to many fields closely related to people's lives, including industrial, military, medical, and daily life. It can be seen that the research of piezoelectric ceramics is of great significance. With the advent of new processes and new materials, piezoelectric ceramics are changing with each passing day. This paper describes some new applications of piezoelectric ceramics. wide application of piezoelectric ceramics are widely used. In general, it can be divided into frequency control, transducer sensing and optoelectronic devices. piezoelectric ceramic frequency control devices include filters, resonators, and delay lines. These devices are used in the tracker, microcomputer, and color TV delay circuits. Piezoelectric ceramic sheets (piezoelectric vibrators) generate mechanical vibration at a certain frequency under the action of an external alternating voltage. In general, the amplitude of such vibration is small, but when the frequency of the applied voltage is the same as the natural mechanical vibration frequency of the piezoelectric vibrator, resonance is caused, and the amplitude is greatly increased. At this time, the alternating electric field generates strain by the inverse piezoelectric effect, and the strain generates a current by the positive piezoelectric effect.

Piezoelectric devices are widely used not only in the industrial and civilian products, but also in military applications. For example, piezo ceramics transducer have been used for ignition for a long time. In 1969, China used piezoelectric materials on piezoelectric fuses, equipped with new 40 rockets, and began mass production. The maximum annual output exceeded 3 million pieces, and the cumulative output in 103 years was more than 20 million pieces. There are nearly 103 varieties, mainly used in armor-piercing projectiles. Other important areas, such as radar, military communications and navigation equipment, requires a large number of piezoceramic filters and piezoelectric SAW filters. As the US technology and market evaluation company recently pointed out in the Tamar report, piezoelectric filters are a basic component that people pay little attention, but are important without them. Modern communications, navigation and defense equipment will not work. This essential role of piezoelectric filter has formed a huge market, and its application continues to expand. Take my case as an example. Developed and produced many types of piezoelectric ceramic filters, piezoelectric SAW filters, SAW delay lines and vibrators for many years; developed and produced various types of piezoelectric accelerometers, piezoelectric gyros, and pressure electric inclinometers, etc.,which have been widely used in military and civilian applications.

2 new devices and new applications

New piezoelectric actuators with high displacement have been increasingly used since the invention of piezoelectric actuators, especially multilayer piezoelectric actuators, especially in precision positioning. Multilayer piezoelectric actuators have been widely used in foreign countries in fuel injection systems and suspension systems. It is well known that techniques for shifting piezoelectric ceramics or electrostrictive piezoceramics include a bending blood tension composite structure, a single wafer, and a dual wafer structure. However, each of these technologies has corresponding limitations in terms of size, mass, maximum displacement, and load bearing capacity. A new single-piece ceramic actuator has been developed that achieves very high axial displacement (1000 μm) and can withstand moderate pressures of approximately 0.6 MPa). The unique structure of this ceramic actuator, called "red" (composed of a reducing layer and an internal offset oxide layer), gives it a stress-strain characteristic that is wider than other structural ranges. The "rain" structure can be made by atmosphere sintering and hot pressing ceramics, especially PLZT piezoelectric and electrostrictive ceramics. For example 2/53/47 (La/Zr/Ti). 5.5/56/44, 8 6/65/35 and 8/70/30. Aydin Dogan and others at the International Actuator and Transducer Center at the University of Pennsylvania have developed marble and dome actuators. The dome actuator consists of a cylindrical piezoelectric ceramic element sandwiched between two frustoconical metal caps, which exhibits a displacement of 40 times that of a ceramic component of the same size and an effective piezoelectric charge coefficient. About 40 times that of PZT itself.

Typical uses for these new ceramic actuators include linear actuators, reciprocating and cavity pumps, switches, loudspeakers, pressure gauges, vibrators, water jets and receivers, optical deflectors, relays, noise reduction and subtraction vibration devices and intelligent systems. In particular, marble and dome actuators have great potential in the automotive industry, they can be used as sensors and damper components, switching elements of valves. The marble actuator is used in the applications where the size is small and the response is fast. It has been successfully used in the optical scanners. High density memory storage drive. Another possible use of a bead type actuator, such as a CDROM drive and a magnetic-optical memory storage drive, is its precise positioning for transport. The marble and dome actuators can also be used in hydrophones, accelerometers and aeroacoustic transducers. Features for different types of piezo ceramic actuators. Piezoelectric and electrostrictive ceramic actuators can be divided into rigid displacement devices and resonant displacement devices. The resonant displacement device is an alternating strain generated by an ac electric field excitation at a mechanical resonant frequency, such as a piezoelectric ultrasonic motor. In order to replace the ordinary electromagnetic motor. Researchers have made many efforts to develop high power ultrasonic motors. Ultrasonic motors are characterized by "low speed and high torque", which is in direct contrast to the high speed and small torque of electromagnetic motors.

The ultrasonic motor currently under the development has a standing wave type and a transmission wave type standing wave type, which is also called a vibration coupler type. The vibrating member is coupled to the piezoelectric actuator to produce a horizontal elliptical motion from the end. In general, the standing wave type has high efficiency, but there is a lack of positive and negative clock direction control problems. Now, a linear ultrasonic motor that combines multiple layers of piezoelectric actuators and tuning fork-shaped metal legs has been developed. Since the mechanical resonance frequency between the two legs is slightly different, the two legs can be controlled by changing the driving frequency. The phase difference between the bending vibrations. Its sliding movement is similar to the horse's use of front and rear legs. When driven with a 6 V voltage of 98 kHz, the test motor with a size of 20 mm × 20 mm × 5 mm has a maximum speed of 20 m/s, a maximum traction of 2 N, and a maximum efficiency of 20% (actuated power of 0.7 W). This motor has been used on precision x-Y platforms.

The transmission mode (surface wave type) combines two kinds of standing waves with two kinds of 90° phase differences on time and space, and has the advantage that both the forward and reverse rotation directions are controllable. By means of the transmission elastic force generated by the piezoelectric ceramics plates, the annular slider which is in contact with the elastic wave surface adhered to the piezoelectric body is driven from two directions by changing the sine and cosine voltage inputs. Another advantage is that the structure is very thin, which makes it suitable for use as an autofocus device in a camera. Canon's "EOS" camera series 80 has been equipped with an ultrasonic motor mechanism.